The Dragon Archive - User contributions [en]

Dragon Notebook

2017-07-09T15:54:24Z

Tormod: /* ERROR MESSAGES AND CODES */ pre

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith, THE EDITOR

== PEEKs, POKES and EXECs ==
<pre>
WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.
</pre>

== Sound and graphics ==
<pre>
SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62
</pre>

== Other ==
<pre>
CONTINUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES
</pre>

=== Addresses of the READ/WRITE routines in ROM. ===
<pre>
00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine
</pre>

== HELPFUL ROUTINES ==

=== RIGHT JUSTIFICATION ROUTINE ===

Where LL is the line length, and string to be justified is A$.
<pre>
10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN
</pre>
AND ANOTHER EXAMPLE
<pre>
10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$
</pre>

=== DISK DRIVE NUMBERS IN PROGRAMS ===

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
<pre>
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
</pre>
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

=== SELECTING MENU OPTIONS ===

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
<pre>
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10
</pre>

=== INVERSE VIDEO ===

(A) Changing text screen to green on black. (D32 AND D64)
<pre>
10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
</pre>
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
<pre>
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253
</pre>

=== AUTO REPEAT ON THE D32 ===

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
<pre>
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)
</pre>

=== DREAM ===

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
<pre>
POKE 29788,215:POKE 29789,145
</pre>
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
<pre>
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
</pre>
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
<pre>
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.
</pre>

=== STRINGS ===

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

=== FILEMASTER ===

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
<pre>
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
</pre>
By adding the following line, the number of each record can be
printed:
<pre>
5587 PRINT#DV,R(LN)+1
</pre>

=== LLISTINGS ===

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

=== BASIC ADDRESSES ===

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
=== DISK FILES ===
<pre>
ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header bytes.
7/8) Exec address -put into &H9D/9E to tell basic where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header, otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.
</pre>

=== TO SAVE GRAPHICS TO TAPE OR DISK ===

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-
<pre>
(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649
</pre>

=== AUTOREPEATING KEYS FOR THE D32 ===

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

=== COLD START ===

A Cold Start can be forced by POKE 113,0 and pressing RESET

=== PAUSE ===

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

=== INVERTING GRAPHICS PAGES ===

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
<pre>
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
</pre>
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

=== RESCUE OPERATION ===

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

=== THREE COLOUR PMODE4 ===

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

=== DISABLE BREAK KEY ===

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

=== SLOW DOWN LIST ===

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

=== EASY MOVING GRAPHICS ===

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
<pre>
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)
</pre>

=== CLEAR SCREEN IN M/CODE ===
<pre>
(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS
</pre>

=== PRINTER LINE FEED ===

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

=== PRINTER FIELD WIDTH ===

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

=== GRAPHICS - HIDING SCREENS ===

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
<pre>
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
</pre>
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

=== TEXT IN M/CODE PROGRAMS ===

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

=== INCREASE MEMORY AVAILABLE ===

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

=== GRAPHICS PAGES - ADDRESSES ===

To find START and END addresses of Graphic Pages in use:-
<pre>
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END
</pre>

=== PRINTER - TO AVOID HANG UPS ===

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

=== PRINTER - PARAMETER SETTING ===

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

=== DRIVE NUMBER ===

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

=== BAUD RATE CODE ===

This short subroutine will fill in the array with the baud
rate associated with the array index:
<pre>
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600
</pre>

=== DATA TROUBLE ===

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

=== AWAIT KEYPRESS ===

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

=== KEYBOARD DISABLE ===

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

=== GRAPHICS (Colour) ===
<pre>
(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)
</pre>

=== TEXT SCREEN ===
<pre>
(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)
</pre>

=== CURSOR - TO REDEFINE ===
<pre>
POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
</pre>
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

=== CASSETTE - HIGH SPEED MODE RESCUE ===

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

=== BREAK - TO DISABLE ===

To turn the BREAK key on and off within a program, use this
subroutine:
<pre>
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6
</pre>
OR AN EVEN SHORTER ROUTINE:
<pre>
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
</pre>
NOTE: These routines do not work during INPUT lines.

=== BREAK - TO DISABLE INCLUDING INPUT LINES ===

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
<pre>
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551
</pre>

=== TELEWRITER ===

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

=== PRINT - VARY OUTPUT TO SCREEN OR PRINTER ===
<pre>
100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)
</pre>

=== CONVERT HEX/DECIMAL/HEX ===

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

=== DISPLAY ===

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

=== LOOPS ===

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

=== CENTERING A TITLE ===

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

=== CASSETTES ===

To load a headerless program - MOTORON: EXEC 46868

=== WAIT FOR KEYPRESS ===

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

=== CASSETTE LOADING ===

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

=== FC (Function Call) errors ===

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

=== OD (Out of data) errors ===

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

=== PAINT errors ===

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

=== USR Routines ===

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.
<pre>
5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
</pre>
where 30000 can be any address......
and then later in the program...
<pre>
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)
</pre>

=== BS Bad Subscript errors ===

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

=== DD Attempt to redimension an array. ===

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

=== DS Direct statement ===

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

=== FM Bad file mode ===

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

=== NE File non-existent ===

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

=== NF NEXT without FOR ===

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

=== TF Too many open ===

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

=== UL Undefined line ===

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

=== DATA ===

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==
NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.
<pre>
MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0
</pre>
NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
<pre>
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour
</pre>

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==
<pre>
65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa
</pre>

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==
<pre>
0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error
</pre>

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:53:24Z

Tormod: /* BAUD RATE CODE */ fixup

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith, THE EDITOR

== PEEKs, POKES and EXECs ==
<pre>
WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.
</pre>

== Sound and graphics ==
<pre>
SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62
</pre>

== Other ==
<pre>
CONTINUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES
</pre>

=== Addresses of the READ/WRITE routines in ROM. ===
<pre>
00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine
</pre>

== HELPFUL ROUTINES ==

=== RIGHT JUSTIFICATION ROUTINE ===

Where LL is the line length, and string to be justified is A$.
<pre>
10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN
</pre>
AND ANOTHER EXAMPLE
<pre>
10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$
</pre>

=== DISK DRIVE NUMBERS IN PROGRAMS ===

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
<pre>
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
</pre>
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

=== SELECTING MENU OPTIONS ===

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
<pre>
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10
</pre>

=== INVERSE VIDEO ===

(A) Changing text screen to green on black. (D32 AND D64)
<pre>
10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
</pre>
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
<pre>
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253
</pre>

=== AUTO REPEAT ON THE D32 ===

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
<pre>
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)
</pre>

=== DREAM ===

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
<pre>
POKE 29788,215:POKE 29789,145
</pre>
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
<pre>
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
</pre>
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
<pre>
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.
</pre>

=== STRINGS ===

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

=== FILEMASTER ===

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
<pre>
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
</pre>
By adding the following line, the number of each record can be
printed:
<pre>
5587 PRINT#DV,R(LN)+1
</pre>

=== LLISTINGS ===

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

=== BASIC ADDRESSES ===

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
=== DISK FILES ===
<pre>
ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header bytes.
7/8) Exec address -put into &H9D/9E to tell basic where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header, otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.
</pre>

=== TO SAVE GRAPHICS TO TAPE OR DISK ===

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-
<pre>
(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649
</pre>

=== AUTOREPEATING KEYS FOR THE D32 ===

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

=== COLD START ===

A Cold Start can be forced by POKE 113,0 and pressing RESET

=== PAUSE ===

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

=== INVERTING GRAPHICS PAGES ===

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
<pre>
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
</pre>
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

=== RESCUE OPERATION ===

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

=== THREE COLOUR PMODE4 ===

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

=== DISABLE BREAK KEY ===

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

=== SLOW DOWN LIST ===

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

=== EASY MOVING GRAPHICS ===

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
<pre>
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)
</pre>

=== CLEAR SCREEN IN M/CODE ===
<pre>
(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS
</pre>

=== PRINTER LINE FEED ===

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

=== PRINTER FIELD WIDTH ===

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

=== GRAPHICS - HIDING SCREENS ===

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
<pre>
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
</pre>
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

=== TEXT IN M/CODE PROGRAMS ===

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

=== INCREASE MEMORY AVAILABLE ===

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

=== GRAPHICS PAGES - ADDRESSES ===

To find START and END addresses of Graphic Pages in use:-
<pre>
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END
</pre>

=== PRINTER - TO AVOID HANG UPS ===

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

=== PRINTER - PARAMETER SETTING ===

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

=== DRIVE NUMBER ===

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

=== BAUD RATE CODE ===

This short subroutine will fill in the array with the baud
rate associated with the array index:
<pre>
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600
</pre>

=== DATA TROUBLE ===

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

=== AWAIT KEYPRESS ===

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

=== KEYBOARD DISABLE ===

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

=== GRAPHICS (Colour) ===
<pre>
(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)
</pre>

=== TEXT SCREEN ===
<pre>
(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)
</pre>

=== CURSOR - TO REDEFINE ===
<pre>
POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
</pre>
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

=== CASSETTE - HIGH SPEED MODE RESCUE ===

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

=== BREAK - TO DISABLE ===

To turn the BREAK key on and off within a program, use this
subroutine:
<pre>
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6
</pre>
OR AN EVEN SHORTER ROUTINE:
<pre>
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
</pre>
NOTE: These routines do not work during INPUT lines.

=== BREAK - TO DISABLE INCLUDING INPUT LINES ===

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
<pre>
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551
</pre>

=== TELEWRITER ===

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

=== PRINT - VARY OUTPUT TO SCREEN OR PRINTER ===
<pre>
100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)
</pre>

=== CONVERT HEX/DECIMAL/HEX ===

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

=== DISPLAY ===

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

=== LOOPS ===

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

=== CENTERING A TITLE ===

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

=== CASSETTES ===

To load a headerless program - MOTORON: EXEC 46868

=== WAIT FOR KEYPRESS ===

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

=== CASSETTE LOADING ===

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

=== FC (Function Call) errors ===

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

=== OD (Out of data) errors ===

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

=== PAINT errors ===

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

=== USR Routines ===

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.
<pre>
5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
</pre>
where 30000 can be any address......
and then later in the program...
<pre>
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)
</pre>

=== BS Bad Subscript errors ===

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

=== DD Attempt to redimension an array. ===

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

=== DS Direct statement ===

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

=== FM Bad file mode ===

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

=== NE File non-existent ===

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

=== NF NEXT without FOR ===

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

=== TF Too many open ===

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

=== UL Undefined line ===

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

=== DATA ===

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==
NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.
<pre>
MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0
</pre>
NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
<pre>
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour
</pre>

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==
<pre>
65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa
</pre>

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:51:42Z

Tormod: /* HELPFUL ROUTINES */ pre and headers

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith, THE EDITOR

== PEEKs, POKES and EXECs ==
<pre>
WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.
</pre>

== Sound and graphics ==
<pre>
SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62
</pre>

== Other ==
<pre>
CONTINUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES
</pre>

=== Addresses of the READ/WRITE routines in ROM. ===
<pre>
00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine
</pre>

== HELPFUL ROUTINES ==

=== RIGHT JUSTIFICATION ROUTINE ===

Where LL is the line length, and string to be justified is A$.
<pre>
10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN
</pre>
AND ANOTHER EXAMPLE
<pre>
10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$
</pre>

=== DISK DRIVE NUMBERS IN PROGRAMS ===

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
<pre>
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
</pre>
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

=== SELECTING MENU OPTIONS ===

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
<pre>
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10
</pre>

=== INVERSE VIDEO ===

(A) Changing text screen to green on black. (D32 AND D64)
<pre>
10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
</pre>
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
<pre>
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253
</pre>

=== AUTO REPEAT ON THE D32 ===

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
<pre>
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)
</pre>

=== DREAM ===

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
<pre>
POKE 29788,215:POKE 29789,145
</pre>
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
<pre>
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
</pre>
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
<pre>
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.
</pre>

=== STRINGS ===

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

=== FILEMASTER ===

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
<pre>
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
</pre>
By adding the following line, the number of each record can be
printed:
<pre>
5587 PRINT#DV,R(LN)+1
</pre>

=== LLISTINGS ===

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

=== BASIC ADDRESSES ===

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
=== DISK FILES ===
<pre>
ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header bytes.
7/8) Exec address -put into &H9D/9E to tell basic where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header, otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.
</pre>

=== TO SAVE GRAPHICS TO TAPE OR DISK ===

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-
<pre>
(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649
</pre>

=== AUTOREPEATING KEYS FOR THE D32 ===

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

=== COLD START ===

A Cold Start can be forced by POKE 113,0 and pressing RESET

=== PAUSE ===

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

=== INVERTING GRAPHICS PAGES ===

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
<pre>
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
</pre>
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

=== RESCUE OPERATION ===

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

=== THREE COLOUR PMODE4 ===

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

=== DISABLE BREAK KEY ===

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

=== SLOW DOWN LIST ===

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

=== EASY MOVING GRAPHICS ===

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
<pre>
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)
</pre>

=== CLEAR SCREEN IN M/CODE ===
<pre>
(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS
</pre>

=== PRINTER LINE FEED ===

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

=== PRINTER FIELD WIDTH ===

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

=== GRAPHICS - HIDING SCREENS ===

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
<pre>
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
</pre>
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

=== TEXT IN M/CODE PROGRAMS ===

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

=== INCREASE MEMORY AVAILABLE ===

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

=== GRAPHICS PAGES - ADDRESSES ===

To find START and END addresses of Graphic Pages in use:-
<pre>
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END
</pre>

=== PRINTER - TO AVOID HANG UPS ===

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

=== PRINTER - PARAMETER SETTING ===

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

=== DRIVE NUMBER ===

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

=== BAUD RATE CODE ===

This short subroutine will fill in the array with the baud
rate associated with the array index:
<pre>
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600
<pre>

=== DATA TROUBLE ===

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

=== AWAIT KEYPRESS ===

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

=== KEYBOARD DISABLE ===

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

=== GRAPHICS (Colour) ===
<pre>
(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)
</pre>

=== TEXT SCREEN ===
<pre>
(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)
</pre>

=== CURSOR - TO REDEFINE ===
<pre>
POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
</pre>
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

=== CASSETTE - HIGH SPEED MODE RESCUE ===

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

=== BREAK - TO DISABLE ===

To turn the BREAK key on and off within a program, use this
subroutine:
<pre>
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6
</pre>
OR AN EVEN SHORTER ROUTINE:
<pre>
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
</pre>
NOTE: These routines do not work during INPUT lines.

=== BREAK - TO DISABLE INCLUDING INPUT LINES ===

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
<pre>
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551
</pre>

=== TELEWRITER ===

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

=== PRINT - VARY OUTPUT TO SCREEN OR PRINTER ===
<pre>
100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)
</pre>

=== CONVERT HEX/DECIMAL/HEX ===

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

=== DISPLAY ===

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

=== LOOPS ===

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

=== CENTERING A TITLE ===

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

=== CASSETTES ===

To load a headerless program - MOTORON: EXEC 46868

=== WAIT FOR KEYPRESS ===

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

=== CASSETTE LOADING ===

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

=== FC (Function Call) errors ===

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

=== OD (Out of data) errors ===

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

=== PAINT errors ===

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

=== USR Routines ===

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.
<pre>
5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
</pre>
where 30000 can be any address......
and then later in the program...
<pre>
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)
</pre>

=== BS Bad Subscript errors ===

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

=== DD Attempt to redimension an array. ===

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

=== DS Direct statement ===

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

=== FM Bad file mode ===

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

=== NE File non-existent ===

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

=== NF NEXT without FOR ===

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

=== TF Too many open ===

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

=== UL Undefined line ===

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

=== DATA ===

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==
NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.
<pre>
MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0
</pre>
NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
<pre>
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour
</pre>

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==
<pre>
65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa
</pre>

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:38:53Z

Tormod: /* PEEKs, POKES and EXECs */ pre

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith, THE EDITOR

== PEEKs, POKES and EXECs ==
<pre>
WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.
</pre>

== Sound and graphics ==
<pre>
SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62
</pre>

== Other ==
<pre>
CONTINUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES
</pre>

=== Addresses of the READ/WRITE routines in ROM. ===
<pre>
00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine
</pre>

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

=== FC (Function Call) errors ===

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

=== OD (Out of data) errors ===

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

=== PAINT errors ===

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

=== USR Routines ===

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.
<pre>
5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
</pre>
where 30000 can be any address......
and then later in the program...
<pre>
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)
</pre>

=== BS Bad Subscript errors ===

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

=== DD Attempt to redimension an array. ===

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

=== DS Direct statement ===

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

=== FM Bad file mode ===

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

=== NE File non-existent ===

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

=== NF NEXT without FOR ===

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

=== TF Too many open ===

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

=== UL Undefined line ===

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

=== DATA ===

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==
NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.
<pre>
MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0
</pre>
NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
<pre>
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour
</pre>

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==
<pre>
65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa
</pre>

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:33:36Z

Tormod: /* INTRODUCTION */

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith, THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

=== FC (Function Call) errors ===

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

=== OD (Out of data) errors ===

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

=== PAINT errors ===

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

=== USR Routines ===

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.
<pre>
5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
</pre>
where 30000 can be any address......
and then later in the program...
<pre>
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)
</pre>

=== BS Bad Subscript errors ===

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

=== DD Attempt to redimension an array. ===

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

=== DS Direct statement ===

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

=== FM Bad file mode ===

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

=== NE File non-existent ===

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

=== NF NEXT without FOR ===

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

=== TF Too many open ===

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

=== UL Undefined line ===

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

=== DATA ===

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==
NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.
<pre>
MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0
</pre>
NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
<pre>
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour
</pre>

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==
<pre>
65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa
</pre>

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:32:02Z

Tormod: /* DEBUGGING HINTS */ make headers

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

=== FC (Function Call) errors ===

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

=== OD (Out of data) errors ===

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

=== PAINT errors ===

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

=== USR Routines ===

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.
<pre>
5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
</pre>
where 30000 can be any address......
and then later in the program...
<pre>
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)
</pre>

=== BS Bad Subscript errors ===

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

=== DD Attempt to redimension an array. ===

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

=== DS Direct statement ===

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

=== FM Bad file mode ===

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

=== NE File non-existent ===

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

=== NF NEXT without FOR ===

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

=== TF Too many open ===

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

=== UL Undefined line ===

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

=== DATA ===

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==
NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.
<pre>
MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0
</pre>
NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
<pre>
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour
</pre>

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==
<pre>
65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa
</pre>

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:28:49Z

Tormod: /* GRAPHIC MODES of the DRAGON and COCO */ pre

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

FC (Function Call) errors

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

OD (Out of data) errors

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

PAINT errors

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

USR Routines

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.

5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
where 30000 can be any address......
and then later in the program...
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)

BS Bad Subscript errors

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

DD Attempt to redimension an array.

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

DS Direct statement

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

FM Bad file mode

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

NE File non-existent

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

NF NEXT without FOR

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

TF Too many open

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

UL Undefined line

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

DATA

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==
NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.
<pre>
MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0
</pre>
NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
<pre>
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour
</pre>

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==
<pre>
65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa
</pre>

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:26:56Z

Tormod: /* SAM CONTROL BITS */

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

FC (Function Call) errors

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

OD (Out of data) errors

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

PAINT errors

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

USR Routines

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.

5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
where 30000 can be any address......
and then later in the program...
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)

BS Bad Subscript errors

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

DD Attempt to redimension an array.

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

DS Direct statement

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

FM Bad file mode

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

NE File non-existent

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

NF NEXT without FOR

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

TF Too many open

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

UL Undefined line

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

DATA

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==

NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.

MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0

NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==
<pre>
65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa
</pre>

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:26:41Z

Tormod: /* INPUT/OUTPUT ROUTINES */

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

FC (Function Call) errors

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

OD (Out of data) errors

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

PAINT errors

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

USR Routines

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.

5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
where 30000 can be any address......
and then later in the program...
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)

BS Bad Subscript errors

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

DD Attempt to redimension an array.

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

DS Direct statement

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

FM Bad file mode

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

NE File non-existent

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

NF NEXT without FOR

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

TF Too many open

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

UL Undefined line

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

DATA

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==

NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.

MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0

NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==
These refer to DRAGONDOS.
<pre>
65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag
</pre>

== SAM CONTROL BITS ==

65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:26:06Z

Tormod: /* BASIC INTERPRETER CODES */ pre

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

FC (Function Call) errors

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

OD (Out of data) errors

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

PAINT errors

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

USR Routines

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.

5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
where 30000 can be any address......
and then later in the program...
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)

BS Bad Subscript errors

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

DD Attempt to redimension an array.

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

DS Direct statement

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

FM Bad file mode

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

NE File non-existent

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

NF NEXT without FOR

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

TF Too many open

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

UL Undefined line

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

DATA

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==

NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.

MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0

NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==
<pre>
32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line
</pre>
From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given
<pre>
33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader
</pre>
THE FOLLOWING ARE DRAGONDOS ROUTINES
<pre>
49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive
</pre>

== INPUT/OUTPUT ROUTINES ==

These refer to DRAGONDOS.

65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag

== SAM CONTROL BITS ==

65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:24:51Z

Tormod: /* DRAGONDOS WORK SPACE */ pre

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

FC (Function Call) errors

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

OD (Out of data) errors

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

PAINT errors

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

USR Routines

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.

5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
where 30000 can be any address......
and then later in the program...
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)

BS Bad Subscript errors

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

DD Attempt to redimension an array.

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

DS Direct statement

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

FM Bad file mode

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

NE File non-existent

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

NF NEXT without FOR

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

TF Too many open

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

UL Undefined line

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

DATA

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==

NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.

MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0

NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==
<pre>
1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.
</pre>

== BASIC INTERPRETER CODES ==

32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line

From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given

33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
Page 34

36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
Page 35

47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader

THE FOLLOWING ARE DRAGONDOS ROUTINES

49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive

== INPUT/OUTPUT ROUTINES ==

These refer to DRAGONDOS.

65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag

== SAM CONTROL BITS ==

65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:24:09Z

Tormod: /* MEMORY MAP DETAILS */ pre

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

FC (Function Call) errors

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

OD (Out of data) errors

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

PAINT errors

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

USR Routines

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.

5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
where 30000 can be any address......
and then later in the program...
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)

BS Bad Subscript errors

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

DD Attempt to redimension an array.

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

DS Direct statement

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

FM Bad file mode

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

NE File non-existent

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

NF NEXT without FOR

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

TF Too many open

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

UL Undefined line

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

DATA

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==

NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.

MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0

NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==
<pre>
0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table
</pre>

DRAGON/COCO KEYBOARD ROLLOVER TABLE
<pre>
Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G
</pre>
RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED
<pre>
346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.
</pre>
The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==

1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.

== BASIC INTERPRETER CODES ==

32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line

From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given

33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
Page 34

36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
Page 35

47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader

THE FOLLOWING ARE DRAGONDOS ROUTINES

49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive

== INPUT/OUTPUT ROUTINES ==

These refer to DRAGONDOS.

65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag

== SAM CONTROL BITS ==

65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:21:26Z

Tormod: /* BIBLIOGRAPHY */ break up a bit

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

FC (Function Call) errors

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

OD (Out of data) errors

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

PAINT errors

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

USR Routines

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.

5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
where 30000 can be any address......
and then later in the program...
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)

BS Bad Subscript errors

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

DD Attempt to redimension an array.

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

DS Direct statement

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

FM Bad file mode

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

NE File non-existent

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

NF NEXT without FOR

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

TF Too many open

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

UL Undefined line

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

DATA

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==

NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.

MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0

NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.

Other books, if you can find them, are:

ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.

PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL

INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.

DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==

0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table

DRAGON/COCO KEYBOARD ROLLOVER TABLE

Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G

RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED

346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.

The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==

1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.

== BASIC INTERPRETER CODES ==

32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line

From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given

33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
Page 34

36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
Page 35

47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader

THE FOLLOWING ARE DRAGONDOS ROUTINES

49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive

== INPUT/OUTPUT ROUTINES ==

These refer to DRAGONDOS.

65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag

== SAM CONTROL BITS ==

65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

Dragon Notebook

2017-07-09T15:19:37Z

Tormod: /* DISKS AND THE DRAGON 64 */ add headers and preformated tags

== INTRODUCTION ==

This Notebook is dedicated to 6809 programmers past, present
and future and in particular to those whose work has
contributed so much to unravelling the secrets of the
DRAGON'S ROM.

The contents have been gleaned from many different sources
over the years and to all contributors, known and unknown,
we offer out heartfelt thanks.

The Editor's gnarled fingers were responsible for the typing
of all the pages in this book using what he considers to be
the best word processor for the 6809 computers, namely
'STYLOGRAPH' operating under OS9. The major drawback to
using this method is that it is not possible to test any of
the routines after they have been typed. Consequently,
although dozens of mistakes have been spotted and corrected,
it is inevitable that a goodly number will have been
overlooked.

While every effort has been made to check the routines
contained in the Notebook it has not been possible in every
case. Should you become aware of mistakes in any of these
subroutines, please write and let the Editor know,
especially if you are able to put matters right. By the same
token, if you know of any subroutine which would be of
interest to your fellow members, please drop the Editor a
line, and he will include it in any future edition. Of
special interest would be short source code routines from
DREAM or other assembler, because nothing teaches you better
to program in machine code than examining experts routines.

The intention of this small publication was to give all our
members as much information as possible about the Dragon and
to a lesser extent the Tandy Coco. There are many members,
new to computing, who have recently acquired a Dragon who
are struggling to find information with which to augment the
Basic Manual. We hope this Notebook will help them produce
worthwhile programs, which they can share with us all
through the pages of DRAGON UPDATE & UP2DATE.

Ray Smith,
THE EDITOR

== PEEKs, POKES and EXECs ==

WAIT for Keyboard input
DRAGON EXEC 34091 (COCO EXEC 44539)
Same as Q$=INKEY$:IF Q$="" THEN 10

HIGH SPEED POKE
POKE 65495,0
Doubles the processing speed from .89mhz to 1.7mhz - useful
for data processing and arithmetical functions, but
POTENTIALLY can be dangerous for your computer as it can
shorten the life of the chips.

POKE 65494,0
Returns computer to normal speed.
Use this poke before inputting or outputting any information
to tape or disk, if you are using the high speed poke.

POKE 65497,0
An even faster speed. Screen image is lost and should be
used with extreme caution with involved arithmetic
calculations only.

POKE 65496,0
Turns off above speed poke.

COLD START
POKE113,0
Produces a cold start whenever the RESET button is pressed.

WARM START
EXEC 40999 (COCO 46004)
Produces a warm start, but if used after the above poke,
will then produce an immediate cold start.

DISABLE LIST COMMAND
POKE 383,158
List command will produce garbage.
Also disables DIR command for disk
POKE&H180,PEEK(114):POKE&H180, PEEK(115)
Disables the List command when using disks only.

TRON/TROFF
POKE175,79
Turns on Trace flag - same as TRON
POKE175,0
Turns it off again - same as TROFF

GRAPHICS MODE
PEEK(182)
Returns present PMODE number.
Returns 0 if graphics not in use.

LOWER CASE CHARACTERS
Coco POKE 282,0. Dragon POKE 329,0
Text will be printed to screen in inverse video and to
printer in lower case.

UPPER CASE CHARACTERS
DRAGON POKE 329,255 (COCO POKE 282,255)
Turns off lower case flag and all text will be in Capitals.

PRINT DISK DIRECTORY
POKE 111,254:DIR
DEVN routine. Decides which device the text output is
directed to.
0=Screen. 255=tape. 254=printer.

TIMER VALUE
PEEK(274)*256+PEEK(275)
Gives the value of the timer.
POKE274,0 and POKE275,0 to return value of Timer to 0.

LAST KEY PRESSED
PEEK(135)
Gives the ASCII code of last key pressed in program.

LAST VARIABLE USED
PEEK(55) + PEEK(56)
Gives ASCII code of last variable used. Print CHR$ in front
of the command to get the STRING value of last variable
used.

PCLEAR0 for DISK
POKE25,PEEK(188):NEW
Will give you an SN error, but PCLEAR0 will have been
accomplished. Or alternatively:-
POWER UP:POKE25,14:POKE26,0:NEW
for the same thing.

PCLEAR0 for TAPE systems
POKE 25,6:NEW

MOTOR ON / MOTOR OFF
POKE 65313,4 for motor on.
POKE 65313,52 for motor off.

MACHINE CODE PROGRAM ADDRESSES
(a) For tape:
START: PEEK(487) * 256 + PEEK(488)
END: PEEK(126) * 256 + PEEK(127)-1
EXEC: PEEK(157) * 256 + PEEK(158)
(b) For disk: (Dragon only)
FOR X=1618 TO 1623 STEP 2: PRINT
PEEK(X) * 256 + PEEK(X+1);:NEXT
The resulting numbers will be:
START, LENGTH and EXEC.
To find END address, add START and LENGTH together and
deduct 1.

BASIC PROGRAM ADDRESSES
PEEK(25)*256+PEEK(26) - START
PEEK(31)*256+PEEK(32) - END

TEXT SCREEN - CURSOR POSITION
PEEK(136)*256+PEEK(137)
Shows a position somewhere between 1024(Start of screen) &
1535(end)

MAXIMUM MEMORY POINTER
PEEK(116)*256+PEEK(117)
Shows end of RAM

HIMEM
PEEK(39)*256+PEEK(40)
Shows place of protected memory, and is highest address for
basic.

CHARACTER TO TEXT SCREEN
POKE (1024-1535),(33-255)
Pokes a character or graphics block to the text screen.

CHARACTER/COLOR BLOCK to GRAPHIC
Applies to PMODE 1 and 2 only.
POKE (1536-4607),(33-255) for tape or POKE
(3072-6143),(33-255) disk.

DISKS
PEEK(235) for DRIVE number.
PEEK(236) for TRACK number.
PEEK(237) for SECTOR number.

TAPE FILENAME of file last loaded

FORX=474TO481:PRINTCHR$(PEEK(X));: NEXT
Prints filename of the last tape file loaded in string form.

TEXT TO SCREEN DISABLE

POKE359,255
After you use this Poke, nothing you type on the keyboard
appears on the screen. Whatever statement you type will be
executed, provided it does not require any text to be
printed on screen. In consequence you can type for example
SCREEN1,1 or PCLS or SOUND100,1 and these will be executed.
The DIR command will not work however, as it requires the
list of files to be printed on the screen. The LIST command
is also disabled.
Do not use this poke in your program if you require
statements to be printed on the screen.
POKE359,126
Although this will not itself appear on the screen, it will
restore the text etc on screen to normal.

ORANGE TEXT SCREEN

POKE359,57
Lets you use any graphic screen or the text screen
(SCREEN0,1) without alternating back to the default text
screen. Consequently SCREEN0,1 will give you an orange
screen without switching back to the normal green screen.
Using SCREEN0,1 after this POKE will make your title screens
have more impact.
POKE359,126 to recover from above.

DRIVE NUMBER FOR DRAGONDOS

Although you can use the command DRIVE 1 (or 2,3 or 4) in
your program. You cannot use a variable (in Dragondos) and
so DRIVE X will produce an error.
You can however use POKE1546,DR where DR is the variable for
any Drive number in the range 1 to 4.

CURRENT LINE NUMBER

PEEK(104)*256+PEEK(105)

CURRENT DATA LINE NUMBER

PEEK(49)*256+PEEK(50)

DISK/TAPE CHECK

PEEK(188)
This returns a 6 if no disk drive is installed for both Dragon
& the Coco. If a disk drive is installed then a 14 is returned
for the Coco and a 12 for the Dragon.

SOUND - OCTAVE

PEEK(222)+1
Returns the current Octave in use.

SOUND - NOTE LENGTH

PEEK(225)
Notes can be any length from 1 to 255.

SOUND - CURRENT TEMPO

PEEK(226)
Tempo can be from 1 to 255.

GRAPHICS - COLORSET

PEEK(193)
Returns 8 if using Colorset 1 or 0 if using Colorset 0.

GRAPHICS - START BYTE

PEEK(186)*256+PEEK(187)
Returns start address at top of current Hi-res screen.

GRAPHICS - END BYTE

PEEK(183)*256+PEEK(184)
Returns end address at the bottom right of current hi-res
screen.

GRAPHICS - CIRCLE RADIUS

PEEK(207)*256+PEEK(208)
Returns the radius of a circle if drawn in PMODE4. Multiply the
number by 2 to get the radius of a circle in PMODE1 and 3.

GRAPHICS - CIRCLE CENTRE

(a) PEEK(203)*256+PEEK(204)
Returns the centre X co-ordinate of a circle in PMODE4,
Multiply by 2 for PMODES1 and 3.
(continued over)

(b) PEEK(205)*256+PEEK(206)
Returns the centre Y (vertical) co-ordinate of a circle in
PMODE4, multiply by 2 for PMODES 1 and 3.

GRAPHICS - DRAW

(a) ANGLE PEEK(232)
Returns Draw angle from 0 to3.
(b) SCALE PEEK(233)
Returns scale number from 1 to 62

CONTNUE after BREAK

PEEK(41)*256+PEEK(42)
Gives the line number at which continuation should begin after
Break.

DISK DIRECTORY

COCO EXEC 52175
DRAGON EXEC 55868
Prints disk directory on screen, same as command DIR.

JOYSTICK - FIRE BUTTON

PEEK(65280)
COCO: Returns 253 or 125 for LEFT joystick fire button and
254/126 if RIGHT joystick button pressed. 255 if no button
pressed and 257 if BOTH are pressed.
DRAGON: returns 253/125 for LEFT joystick,254/126 Right
joystick, 255/127 if no button pressed and 252 for both.

TAPE: LOADING A HEADERLESS PROGRAM

MOTORON: EXEC &HB714
This should load in a program which has been saved, for
example, when the motor did not get up to speed in time and so
you've got a program saved without a header.

TAPE: SLOW STARTING AUTOMATICS

If your tape recorder is slow to start when it receives the
signal, remove the remote jack and switch the motor on from the
program, or in direct mode with MOTORON:SOUND1,20:
CSAVE"PROGRAM". This is the method used by Harvey Grey, and as
he says it never fails.

TAPE: MERGING TWO PROGRAMS

Have the two programs ready, by renumbering Program B so that
its line numbers start after those of Program A.
CLOAD"PROGRAMA":POKE25,PEEK(27):POKE26,PEEK(28)-2:
CLOAD"PROGRAMB":POKE25,30:POKE26,1
They should then have merged.

ERASE - ANY PROGRAM IN MEMORY

DRAGON EXEC 33815 COCO EXEC 44313
Erases any program - same as the NEW command

CUMANA DOS POKES

Addresses of the READ/WRITE routines in ROM.

00EB Number of the active drive
00EE/F Buffer address (for sector read/write)
00F6 If non-zero decrement 0605 in each IRQ
0605 When reaches zero turns off disk motor
0609 Verify flag: 0=Off else is On
060A Drive number
0697/8 Auto current line number
0699/A Auto increment
069B Auto flag: 0=Off else is on
069C/D Error GOTO - line number
069E Error GOTO flag: 0=off else is on
069F/A0 ERL
06A1 ERR
E56D Sector READ routine
E643 Sector WRITE routine

== HELPFUL ROUTINES ==

RIGHT JUSTIFICATION ROUTINE

Where LL is the line length, and string to be justified is A$.

10 LL=51:P=51
20 DF=LL-LEN(A$):IF INSTR(A$,"")=0 THEN80
30 IF DF=0 THEN80
40 FOR J=P TO1STEP-1:IF MID$(A$,J,1)="" THEN A$=LEFT$(A$,J)+
MID$(A$,J):DF=DF-1:GOTO60
50 NEXT
60 P=J-1:IF P<1 THEN P=LEN(A$)
70 GOTO30
80 RETURN

AND ANOTHER EXAMPLE

10 A$="This is just an example of a string"
20 A$=A$+""
30 LL=32:F=0:S=0:N=0:P=1:L=LEN(A$):B$=""
40 GOSUB180:GOSUB190:IF F=0 THEN70
50 S=S-P+F:P=F
60 IF P>=L THEN N=N+1:GOTO40
70 IF N=1 THEN210
80 P=1:GOSUB180
90 SP=LL-S-P-N+2
100 B$=B$+STRING$(P-1,32)
110 DS=INT(SP/(N-1)):MS=SP-(N-1)*DS:PA=1
120 GOSUB190:IF F=0 THEN200
130 B$=B$+MID$(A$,P,F-P):P=F
140 GOSUB180
150 IF SP=0 THEN B$=B$+" ":GOTO120
160 IF PA>=MS THEN B$=B$-STRING$(DS+2,32):SP=SP-DS-1:PA=PA+1:
GOTO120
170 B$=B$+STRING$(DS+1,32):SP=SP-DS:GOTO200
180 IF MID$(A$,P,1)=" " THEN P=P+1:GOTO180:ELSE
RETURN
190 F=INSTR(P,A$," "):RETURN
200 B$=LEFT$(B$,LL)
210 A$=B$:PRINT A$

DISK DRIVE NUMBERS IN PROGRAMS

You can use specified drive numbers in programs, using the
command DRIVE n, where n is a number from 1 to 4; but you
cannot specify a variable with this command.
You can input a variable and use it as part of the READ/WRITE
commands, as follows:
100 INPUT"drive number";D
110 FWRITE CHR$(48+D)+":FILENAME.DAT";variable list
Alternatively you can set the default drive to whatever number
from 1 to 4 you specify, with a
poke: eg POKE 235,D or POKE1546,D personally I always use the
latter.

SELECTING MENU OPTIONS

Suppose the option required is in A$ and they are sequential,
A, B, C etc, then:- ON ASC(A$-64) GOTO 100,200,300,etc.
If they are NOT sequentioal, ie A,L,M,S,X etc
10 A$=INKEY$:IF A$="" THEN 10
20 ON INSTR(A$,"ALMSX etc")GOTO100,200,300 etc
30 PRINT"INVALID OPTION":GOTO10

INVERSE VIDEO

(A) Changing text screen to green on black. (D32 AND D64)

10 CLEAR200,32539
20 FORX=32540 TO 32635:READ A$
30 POKEX,VAL("&H"+A$):NEXT
40 FOR X=0TO127:PRINT@0,CHR$(X):POKEX+32627,PEEK(1024):NEXT
50
POKE359,126:POKE360,127:POKE361,28:POKE416,126:POKE417,127:POKE
418,109:CLS
60 DATA32,62,34,36,9E,88,81,8,26,D,8C,4,0,27,35,86,20,A7,84,A7,
82,26,15,81,D,26,4,8D,29,20,D,4D,2B,8,10,8E,7F,7D,A6,A6,88,40,
A7,80,9F,88,8C,5
70 DATA FF,23,11,8E,4,0,EC,88,20,ED,81,8C,5,E0,25,F6,9F,88,8D,
2,35,B6,86,20,A7,80,1F,10,C4,1F,26,F6,39,2F,1,39,35,10,8C,BA,62
,26,F8,C6,20,7E,BA,79
CLS WILL WORK OKAY, BUT CLEAR OR RESET WILL RESULT IN THE
SCREEN REVERTING TO BLACK ON GREEN

(B) Green or orange on black for D64 only.

Enter 64 mode & run following basic program: This caters for
CLS and RESET and sets to an orange screen if you enter SCREEN
0,1
10 POKE 59735,15
20 POKE 62659,32
30 POKE 63992,32
40 POKE 64423,32
50 POKE 64447,32
60 POKE 64470,8
70 POKE 64474,2
80 POKE 64475,128
90 POKE 64476,96
100 POKE 283,105
110 POKE 284,253

AUTO REPEAT ON THE D32

Although the D64 has autorepeat in the 64 mode, the D32
keyboard will auto repeat with the following subroutine:
10 POKE &HFF04,(PEEK(&HFF03)AND &HFE)
20 POKE &H10D,&HBF:POKE &H10E,&H20
30 POKE &HFF03,(PEEK(&HFF03)OR 1)

DREAM

To make it easier to save source code to tape, as the header
used in Dream is too short for some recorders which have
trouble getting up to speed in time.
POKE 29788,215:POKE 29789,145
This lengthens the header tone, but slows up the recording
slightly.

IF THIS STILL DOES NOT WORK, TRY THE FOLLOWING:
EXIT from Dream with BREAK/Q and when in Basic type the
following:
CSAVEM"FILENAME",PEEK(&H5F8A)*256+PEEK(&H5F8B),&H6000,&H6080
Press PLAY & RECORD on Cassette recorder and then PRESS ENTER.
To RELOAD into Dream:
a) Load Dream but don't EXEC.
b) CLOAD"FILENAME"
c) EXEC
d) Reply 'Y' to 'Old text?' prompt.

STRINGS

When you use temporary variables in programs, such as
X$=INKEY$, use the same variables over and over again,
otherwise you can get an OS (out of string space error).
You can force a Garbage collection by using EXEC36055. This
makes the computer sort out the string space.

FILEMASTER

When you wish to update a file and save it with the same name,
the program justs tags the updated file on the end of the old
file, rather than killing the old file first. You can get over
this problem by changing the following lines in OLDFILE.
3640 MN$+NM$+"DAT":KILL MN$:FWRITE NM$;RL
8005 GOTO 3640
By adding the following line, the number of each record can be
printed:-
5587 PRINT#DV,R(LN)+1

LLISTINGS

To printout listings in the same width as the Dragon screen (ie
32 characters per line) - POKE &H148,0:POKE &H9B,32:LLIST

BASIC ADDRESSES

START ADDRESS: STADR=PEEK(25)*256+PEEK(26)
END ADDRESS: ENADR=PEEK(27)*256+PEEK(28)-1

,CE 1
DISK FILES

ASCII TEXT FILES
Last byte is always "1A".

BASIC FILES
DRAGON - Start with a 9 byte header
1) 55(hex)
2) File type 01 Basic etc, 02 M/code
3/4) Load Address
5/6)Length of program ie length of file less 9 header
bytes.
7/8) Exec address -put into &H9D/9E to tell basic
where to start execution
9) AA(hex)
Bytes 1 & 9 are used by Basic to identify the header,
otherwise the DOS assumes its a DATA file.
End with 3 NULL bytes - 00,00,00

NON-SEGMENTED M/L FILES
DRAGON - as for basic above.
COCO - Start with a 5 byte header.
a) Null byte 00
b) 2 bytes which specify number of data bytes in
program -ie length in Hex
c) 2 bytes which specify start (LOAD) address
- End with a 5 byte tail sequence.
a) FF byte
b) 2 null bytes 00,00
c) 2 bytes which specify EXEC address
- Note - the End address is not stored, but is calculated
from LOAD address plus file length minus 1.

SEGMENTED M/L FILES
COCO - Same as for non-segmented files, but at the end of
every segment they have ANOTHER header and so on. They only
have one END sequence and ONE EXEC address.

TO SAVE GRAPHICS TO TAPE OR DISK

If you do not know the address of the page in
use you can save the currently displayed graphic
page in any PMODE with the following:-

(C)SAVE(M)"FILENAME",PEEK(186) *
256+PEEK(187),PEEK(183) * 256 + PEEK(184),33649

AUTOREPEATING KEYS FOR THE D32

FOR X=337 TO 345: POKE X,255: NEXT: X$=INKEY$

COLD START

A Cold Start can be forced by POKE 113,0 and pressing RESET

PAUSE

EXEC 41194 can be used on the D32 and the D64 in 32 mode to
pause a program, eg following a page of instructions.
Pressing any key restarts the program.

INVERTING GRAPHICS PAGES

This short machine code subroutine will invert the first four
pages of the graphic screens. That is change the foreground
colour to the background colour and vice versa.
To operate EXEC&H6000 or EXEC 24576.
110 FOR X=24576 to 24595
120 READ A$:POKE X,VAL("&H"+A$): NEXT X
130 DATA 8E, 06,00,A6,84,88,FF,A7,84,30,01,8C,1E,00,27,03,7E,
60,03,39
The Data underlined refer to the addresses of the start and
end of the first four graphic pages, when using cassette. If
you are using DISKS then replace with 0C,00 and 24,00.

RESCUE OPERATION

Sometimes when using a mixture of BASIC and M/code routines
you can cause a crash when the Dragon freezes. The only
option being to press RESET. On occasions after pressing
RESET and typing LIST, all you get are the first few lines of
the BASIC program followed by garbled lines.
To get your program back simply type RENUM.
You will be unable to RUN it, but you can SAVE it and reload
after a COLD START.

THREE COLOUR PMODE4

10 PMODE3,1:SCREEN1,1:POKE 65314,248
This line tells BASIC that the four colour mode is required,
but the POKE tells the VIDEO chip that 2 colour high
resolution is wanted.
The new colour set has 0 = WHITE, 1 = BLACK and 2 = LIGHT
PURPLE

DISABLE BREAK KEY

Enter the following Pokes in DIRECT mode:
POKE 411,228: POKE412,203: POKE 413,4: POKE 414,237: POKE
415,228
THEN to DISABLE POKE 410,236
And to ENABLE POKE 410,57

SLOW DOWN LIST

POKE 359,60 - This effects everything that is OUTPUT
including PRINTING. POKE 359,57 for NORMAL SPEED.

EASY MOVING GRAPHICS

First DRAW the shape you want and put it in a STRING
variable, eg C$. Then assign a couple of variables re the
LOCATION and DRAW your shape at the desired location.
10 PMODE4,1:SCREEN1,1:PCLS
20 C$="D6F4H4G4E4U3R3L6R3U3R1D1L2U1R1"
30 X=128:Y=96
40 DRAW"BM"+STR$(X)+","+STR$(Y)+C$
and to move the man, change line 30 as follows
30 FOR X=10 TO 250 STEP 4: Y=96
50 PCLS:NEXT X
60 EXEC34091 (to hold graphics in view)

CLEAR SCREEN IN M/CODE

(A) by using existing ROM routine:
LDB #$60
JSR 47737
RTS
(b) this is the faster way:
LDX #$0400
LDU #$0600
LOOP STU ,X++
BNE LOOP
RTS

PRINTER LINE FEED

If your Printer does not give an automatic line feed, or if
its been turned off for OS9, STYLO etc. POKE330,2 and POKE
330,1 to turn it off again.

PRINTER FIELD WIDTH

To alter the comma field width (default 16), POKE 153, with
the new field and POKE 154 with the last field.
Eg: For 6 fields of length 10, POKE 153,10: POKE154,50
Useful for printing columns, but dont use the value 0,which
makes the Printer hang!

GRAPHICS - HIDING SCREENS

You can hide Graphics Screens behind Loading Screens,
providing you DIM correctly.
PMODE 0 DIM 307 per screen
PMODE 1 & 2 DIM 614 per screen
PMODE 3 & 4 DIM 1228 per screen
GET(0,0)-(255,191),A,B,C etc and PUT back when required.

TEXT IN M/CODE PROGRAMS

To check for text in long machine code programs, eg
Adventures etc, to look for clues?
FOR X=0 TO &H7FFF:PRINT CHR$(PEEK(X));: NEXT

INCREASE MEMORY AVAILABLE

To increase memory available to the maximum when using DISKS,
ie to perform a PCLEAR 0 - No graphic pages.
COCO: POKE 25,14: POKE 3584,0: NEW
DRAGON: POKE 25,12:POKE3072,0: NEW
This gives 28967 available bytes of memory

To increase memory when not using disks - POKE 25,6: NEW
before loading cassette

GRAPHICS PAGES - ADDRESSES

To find START and END addresses of Graphic Pages in use:-
PRINT PEEK(186)*256+PEEK(187) - for the START
PRINT PEEK(183)*256+PEEK(184) - for the END

PRINTER - TO AVOID HANG UPS

Insert the following line in your program to ensure that your
printer is on line, so that the program will not 'hang'.
P=PEEK(65314) AND 1: IF P=1 THEN PRINT"PRINTER NOT ON LINE"

PRINTER - PARAMETER SETTING

Characters per line PEEK(155) - Default 132
To alter to 80 or even 40 etc POKE 328,0: POKE 155,80 or
whatever.

DRIVE NUMBER

Some Dragons will allow you to use DRIVE and the number in
programs, but if you get an error, use POKE&H60,2 or number.

BAUD RATE CODE

This short subroutine will fill in the array with the baud
rate associated with the array index:
DIM BD(15)
FOR X=1 to 15: READ BD(X):NEXT
DATA
50,75,110,135,150,300,600,1200,1800,2400,3600,4800,7200,9600

DATA TROUBLE

When using HEX loaders etc, to find the line number of the
last DATA statement loaded:
PRINT PEEK(49)*256+PEEK(50)

AWAIT KEYPRESS

If two keypresses are required then EXEC41184 (otherwise
EXEC34091)

KEYBOARD DISABLE

(A) POKE 65281,50 (B) POKE 65301,0
AND POKE 65301,20 TO ENABLE AGAIN (from the program!)

RESET - TO DISABLE - POKE 113,85

GRAPHICS (Colour)

(a) Striped effects -
Poke 178,N:LINE(X,Y)-(X1,Y1),PSET,BF
(b) Foreground colour - PEEK (178)
(c) Background colour - PEEK (179)
(d) Active colour - PEEK (180)
(e) Graphic Mode - PEEK (181/2)

TEXT SCREEN

(a) Move to lower half of screen - POKE 136,5
(b) Move to upper half of screen - POKE 136,4
(c) Cursor position in Low-res - PEEK (136/7)
(d) ASCII code of last keypress - PEEK (135)

CURSOR - TO REDEFINE

POKE 363,(ASCII code of required character):
POKE 364,167:
POKE 365,159: POKE 366,0: POKE 367,136
To ACTIVATE above - POKE 362,134 and to DEACTIVATE
POKE362,57

CASSETTE - HIGH SPEED MODE RESCUE

If you accidentally CSAVE a program while in the High Speed
mode then load it back at normal speed then:
POKE 146,8: POKE 147,4: POKE 148,8

BREAK - TO DISABLE

To turn the BREAK key on and off within a program, use this
subroutine:
10 CLEAR 300, 32735
20 FOR X = 32736 TO 32756
30 READ A$: A=VAL("&H"+A$)
40 POKE X,A: NEXT
50 POKE 411,127: POKE 412,224
60 PRINT"BREAK DISABLED": POKE 410,126
70 FOR DL=1 TO 2500:NEXT
80 CLS: PRINT "BREAK ENABLED": POKE 410,57
90 FOR DL=1 TO 2500: NEXT: GOTO60
100 DATA
32,62,1C,AF,BD,80,06,26,07,81,13,26,03,7E,85,2B,
97,87,7E,84,A6

OR AN EVEN SHORTER ROUTINE:
10 FOR X=&HF8 TO &HFE: READ A: POKE X,A:NEXT
20 FOR X=&H19A TO &H19C: READ A: POKE X,A: NEXT
30 DATA 50,98,28,175,126,173,165
40 DATA 126,0,248
NOTE: These routines do not work during INPUT lines.

BREAK - TO DISABLE INCLUDING INPUT LINES

This short M/code subroutine will disable the BREAK key,
including during INPUT lines.
10 CLEAR 200, 32550
20 FOR X-0 TO 55: READ A$: POKE32551+X,VAL("&H"+A$): NEXT
30 DATA 8E,7F,3C,BF,01,6B,8E,7F,54,BF,01,9B,86,7E,B7,01
6A,B7,01,9A,39,0D,6F,27,01,39,32,62,34,14,BD,80
09,BD,80,06,27,F8,81,03,27,F4,7E,B5,42,9F,DF,35
10,30,04,34,10,9E,DF,39
40 EXEC 32551

TELEWRITER

For those who have the Cassette version, you can change the
colour set and have a green on black screen by POKE
&H2FDF,240 before loading.

PRINT - VARY OUTPUT TO SCREEN OR PRINTER

100 INPUT"OUTPUT TO GO TO SCREEN OR PRINTER"; A$
110 A$=LEFT$(A$,1)
120 IF A$="S" THEN P=0:GOTO(Screen Print routine at 150 etc
using PRINT#P)
130 IF A$="P" THEN P= -2 ELSE GOTO100
140 PRINT#P,(Your Printer routine)

CONVERT HEX/DECIMAL/HEX

Let the DRAGON (a) work it out: DECIMAL/HEX ? HEX$(n)
HEX/DECIMAL ? VAL(&Hetc)
(b) add them for you ? HEX$(&H0A+&HFF)

DISPLAY

To change the TEXT screen from GREEN to ORANGE, in order to
highlight instructions etc - POKE 65314,13

LOOPS

Use FOR/NEXT loops in preference to GOTO for Speed and
Efficiency.

CENTERING A TITLE

CLS: PRINT TAB((X-LEN(A$))/2)A$
Where A$ is the Title and X is the number of characters per
screen line/printer line.

CASSETTES

To load a headerless program - MOTORON: EXEC 46868

WAIT FOR KEYPRESS

If you use EXEC 34091, The Key pressed can be read from the
A Register.
EXEC 34091: X$= INKEY$: PRINT X$
or get value of X$ with Y=ASC(X$)-48 (for numbers 1 to 9)

CASSETTE LOADING

To resurrect programs accidentally saved at the faster speed
(POKE 65495,0).
Load the program back using the double speed poke.
AUDIO ON: POKE65497,0: CLOAD
You lose video at this speed and so the Audio is on to tell
you when the tape has finished loading. Press RESET and try
listing program. If the DRAGON does not return to normal mode
POKE 65495,126 and then list. The program sometimes
unfortunately is not recoverable.

== DISKS AND THE DRAGON 64 ==

=== (A) DETACH DOS ===

Unplug your DOS using Software instead of manually unplugging
the cartridge and risking damaging the connections.
<pre>
1 CLS7:PCLEAR4
2 POKE1541,2
3 FOR X=0 TO 146:POKE3073+X,PEEK(46010+X):NEXT
4 POKE 3072,18:POKE3197,0
5 FOR X=1 TO 3: READ S,F: FOR J=S TO F: READ A$
6 POKE 3072+J,VAL("&H"+A$)
7 NEXT J,X
8 DATA 148,156,8E,0C,9C,BD,90,E5,7E,83,71,157,188
9 DATA 44,4F,53,20,44,45,54,41,43,48,20,28,43,29,20,31,
39,38,35,20,44,52,41,47,4F,4E,20,55,53,45,52,00
10 DATA 13,17,8E,7F,FE,20,0E
11 POKE 114,12:POKE 115,0
12 PRINT@224,STRING$(32,236);
13 PRINT@256," PRESS RESET TO DETACH DOS "
14 PRINT@288,STRING$(32,227);
15 SCREEN 0,1
16 GOTO16
</pre>
TO 'UNPLUG' DOS, RUN PROGRAM and press RESET on cue.
TO REGAIN DOS, POKE 113,0 and press RESET.

=== (B) MOVING BASIC AND DOS TO HIGH MEMORY ===

Enabling DISKS to be used in the D64 mode and giving a
further 8k available for program storage from 57344 onwards.
M/code source - assemble in DREAM etc.
<pre>
ORCC #255 Disable IRQ's
LDX #32768 Start of Basic
LOOP STA $FFDE ROM mode
LDA ,X Get byte from ROM
STA $FFDF RAM mode
STA ,X+ Store in RAM
CMPX #57344 All copied
BLO LOOP No Branch again
ANDCC #255-16 Enable IRQ's
RTS Return to Basic in 64k mode
</pre>
This produces through DREAM the following Data:
<pre>
1 CLEAR 600
2 FOR A=1 to 18
3 SREAD 1,16,A,A$,B$
4 SWRITE 1,20,A,A$,B$
5 NEXT
</pre>
If that doesn't accomplish it, which means that Track 16
was also corrupted, then hard luck! You'll either have to
reformat the disk or rebuild the Directory Track, using a
DISK FIXIT type program. Try Pam D'Arcy's program 'DISKFIX'
from the NDUG.

=== (D) CARTRIDGE INTERFACE ===

ODD number lines are on the UPPER side and are all GROUND.
EVEN numbered lines are on the LOWER side.
Looking down on the Cartridge Edge connector the pins run
from 2 to 34, from right to left.
<pre>
2
4
6
8 INDEX
10 DRIVE 0
12 DRIVE 1
14
16 MOTOR
18 DIRECTION
20 STEP
22 WRITE DATA
24 WRITE GATE
26 TRACK 0
28 WRITE PROTECT
30 READ DATA
32 SIDE 1
34 READY - Not connected in Dragondos
</pre>

=== (E) DISK - TO PRINT DIRECTORY ===

POKE 111,254:DIR

=== (F) DISK - DELTADOS ===

This POKE allows long BASIC programs to be run without OM
errors.
LOAD program and if it does not contain a CLEAR statement,
insert at the beginning of the program:-
POKE 377,57: CLEAR 200, &H7FFF
Otherwise just insert the POKE on its own.
NOW SAVE TO DISK and then RUN. If the DOS space was not
overwritten when the program was run, then the DOS can be
RE-ENABLED with POKE 377,126:CLEAR 200,&H78FF.

== GRAPHICS - FINDING CO-ORDINATES ==

To convert PMODE4 co-ordinates (X,Y) to PRINT ` positions on
the TEXT screen:
P=INT(X/8)+32*INT(Y/12): PRINT P: PRINT@P,"*";

== LIST ==

=== (A) TO SLOW DOWN ===
The more common method but NOT TO BE USED WITH DOS OR ANY
CARTRIDGE in place.
POKE 359,19 and if still too fast POKE 360,19 also.
RESET by poking a value of 57 to both locations.

=== (B) TO DISABLE ===
POKE 383,157: POKE 383,158
To re-enable POKE 383,126

== Program loading tricks ==

=== FINDING ADDRESS OF M/CODE PROGRAM ===
<pre>
PRINT PEEK(487)*256+PEEK(458) ......(A)
PRINT PEEK(126)*256+PEEK(127)-1 .....(B)
PRINT PEEK(157)*256+PEEK(158) ......(C)
SAVE OR CSAVEM"PROGRAM", A, B, C
</pre>

=== TO DISABLE AUTORUN PROGRAMS ===

CLOADM"PROGRAM", 1298
CSAVEM"PROGRAM", A+1298, B+1298, C+1298

=== TO RELOCATE MACHINE CODE PROGRAMS ===

(A) ON DISK - LOAD "PROGRAM.BIN", n
(B) ON TAPE - CLOADM"PROGRAM", n
Where 'n' is the offset, found by subtracting the old address
from the new address, providing the new address is higher
than the original address.
If the new address is below the original address than the
value of 'n' = 65536 plus new address less original address.

=== TAPE LOADING DIFFICULTIES ===
Before saving to cassette:
<pre>
POKE &H745B,255: POKE144,1 To raise output signal level
POKE144,3: POKE 144,0 to return to default setting.
POKE &H746b,128 for a longer header.
(or try values between 1 & 255)
POKE 65313,8 Motor on
POKE 65313,247 Motor off
EXEC &H8015 Turns on Cassette relay
EXEC &H8018 Turns it off
</pre>

=== ARROW KEYS ===
Checking that one of the four arrow keys has been used:
<pre>
10 IF INKEY$=CHR$(8) OR CHR$(21) THEN GOTO...(LEFT ARROW)
20 IF INKEY$=CHR$(9) OR CHR$(93) THEN GOTO...(RIGHT ARROW)
30 IF INKEY$=CHR$(10)OR CHR$(91) THEN GOTO...(DOWN ARROW)
40 IF INKEY$=CHR$(94)OR CHR$(95) THEN GOTO...(UP ARROW)
</pre>
The second CHR$ character is SHIFT plus the ARROW key.

== GRAPHICS - HINTS and ROUTINES ==

OVERLAYING ONE SCREEN ON ANOTHER

The basic method is to PCLEAR8 and load one screen into Page
1 and the other into Page 5 (using Hi-res screens, then GET
the picture and PUT it over the Page 1 screen.

10 PCLEAR8
20 PMODE4,1:SCREEN1,1:PCLS
30 LOAD "PICTURE1.EXT" 'for disk
35 CLOADM"PICTURE1" 'for tape
40 PMODE4,5:SCREEN1,1:PCLS
50 LOAD"PICTURE2.EXT",9216 'or
55 CLOADM"PICTURE2",6144 'tape
60 DIM A(160):GET(0,0) - (255,191),A,G
70 PMODE4,1:PUT(0,0)-(255,191),A,AND
80 GOTO80

(FOR PMODE3 SCREENS USE 'OR' IN LINE 70 INSTEAD OF 'AND'.)

EXTRA PAGES ON DRAGON 32

These extra pages are Pages 17 to 20 and work on the D32,
but not apparently on the D64. On the latter machine pages
can be stored in high memory.
PCLEAR8
PMODE4,1:SCREEn1,1
(C)LOAD(M)"PICTURE1"(.EXT")
FORX=1TO4:PCOPY X TO X+4:NEXT
(I.E.) Put it into Page 5 on.
(C)LOAD(M)"PICTURE2"(.EXT")
FORX=1TO4:PCOPY X TO X+16:NEXT
(C)LOAD(M)"PICTURE3"(.EXT")
You should now have 3 pictures in memory and to see them
....
EXEC41194 'Picture 3 visible
FORX=1TO4:PCOPY X+16 TO X:NEXT
EXEC41194 'Picture 2 on screen
FORX=1TO4:PCOPY X+4 TO X:NEXT
EXEC41194 'Picture 1 is back!

DRAW COMMAND

The Draw command always starts by fixing a point on screen
from which to draw and this point can be defined by
variables.
This command usually reads:
DRAW"BM"+STR$(X)+","+STR$(Y) etc
and most people tend to leave out that comma.
The DRAGON will perform the same function using the simpler:
DRAW"BM=X;=Y;" etc
Where X is the horizontal and Y is the vertical co-ordinate
in pixels.

You can MOVE your graphic by simply putting the co-ordinates
in a loop.

HI-RES SCREEN FLIPPER

This Basic sub-routine will flip the screen upside down.
10 DIM A(10),B(10)
20 PMODE4,1:SCREEN1,1
30 FORX=0TO95:GET(0,X)-(255,X),A
,G:GET(0,191-X)-(255,191-X),B,G
40 PUT(0,X)-(255,X),B,PSET: PUT (0,191-X)-(255,191-X),A,PSET
50 NEXT
60 EXEC41194

GET/PUT: SIZE OF DIM REQUIRED

Count the number of bytes used in your graphics. There are
1536 per graphics page, or 6144 in a PMODE3 or PMODE4 4
page screen, but only 3072 in PMODEs 1 and 2.
So take this number and divide by 20 for the odd PMODEs (1 &
3) and divide by 40 for the even modes (2 & 4) then
subtract one.
The result is the length of the one dimensional array
required to store the picture. The same applies to portions
of a screen.
For example half the entire PMODE4 screen (3072 pixels)
would require a DIM of :
(3072/40)-1 or 76

== SCREEN ADDRESSES (GRAPHICS) ==

These depend whether you are using a disk operating system,
as most DOS use the first page of graphics and so with DOS
in place graphics start one page higher.

Page Tape Disk
1 &H0600-&H0BFF &H0C00-&H11FF
2 &H0C00-&H11FF &H1200-&H17FF
3 &H1200-&H17FF &H1800-&H1DFF
4 &H1800-&H1DFF &H1E00-&H23FF
5 &H1E00-&H23FF &H2400-&H29FF
6 &H2300-&H29FF &H2A00-&H2FFF
7 &H2A00-&H2FFF &H3000-&H35FF
8 &H3000-&H35FF &H3600-&H3BFF

To save and load screens to tape use the above scale as
follows for PMODE4 for example:
CSAVEM"FILE",&H600,&H1DFF,&H0600
or in decimal this would be:
CSAVEM"FILE",1536,7679,1536
CLOADM"PIX"

But to save screens to disk you need to save one more byte,
else the byte in the bottom right hand cormer of the screen
will not be saved. Eg:-
SAVE"FILE",&HC00,&H2400,&HC00
which will save it to the default extension ".BIN", but if
you wish to distinguish your graphic screens from machine
code programs save them with an extension such as ".PIX".
In decimal this would be:
SAVE"FILE.PIX",3072,9216,3072. (Superdos 9215)

== DEBUGGING HINTS ==

FC (Function Call) errors

These usually occur in the GET, PUT, DRAW, PLAY and LINE
commands.
An FC error usually means that you are asking one of these
commands to do something they cannot do, and the most likely
causes are:
(a) Co-ordinates out of range. For example horizontal and
vertical must be positive with horizontal less than 256 and
vertical less than 192.
(b) Dimensions of PUT command may be more than the GET
statement.
(c) Execution of a string with an illegal character in it.
For example DRAW"BM100,100;XL$(2);" - where there is nothing
wrong with the DRAW command as such - but on looking back at
XL$(2) you find this = "D2L2P2" - in other words it contains
an illegal character in it, ie "P2".
(d) The most common causes of this error are not necessarily
found in the line in question, but you should look back at
the definition of the individual components.

OD (Out of data) errors

These occur as a rule when you:-
(a) repeat or omit data statements
(b) or you write or copy hexloader addresses wrongly.

PRINT PEEK(49)*256+PEEK(50) will give you the line number of
the current DATA statement.
PRINT PEEK(51)*256+PEEK(52) will give you the address of the
next item in the current Data statement.

PAINT errors

Paint errors can be catastrophic in graphics, when the paint
spreads everywhere and while an error is NOT reported, it
figures that you will not be too happy with the mess it
causes!
If you don't know which particular PAINT command is the
trouble, find where the previous SCREEN command is situated
(say line 100) and put a GOTO100 before each PAINT command
until you locate the one at fault.
Then check the co-ordinates and colour codes for validity,
the co-ordinates must be INSIDE the area you wish to paint.
If this should fail then check the lines where that
particular graphic shape was formulated and ensure that the
outline is completely closed off. Check for a one pixel gap
in the outline somewhere.

USR Routines

A well known bug in the ROM of the Dragon 32 means that the
USR command must contain a zero before each numbered USR
function, but this was corrected in the Dragon 64 and the
zero in that machine causes an error.
No zero in the 32, or a zero in the 64, both show an error.
The following routine inserted in your programs will
circumvent this and will ensure the program should run on
both machines.

5 VS$=CHR$(PEEK(49052) + PEEK(49053)) 'TO TEST WHETHER
DRAGON 32 OR 64
6 IF VS$="64" THEN DEF USR1=30000 ELSE DEF USR01=30000
where 30000 can be any address......
and then later in the program...
IF VS$="64" THEN X=USR1(A) ELSE X=USR01(A)

BS Bad Subscript errors

These usually occur when the subscripts in an array are out
of range. Use a DIM statement to dimension the array. For
example, if you have X$(12) in your program but you have not
informed the computer of the 12 elements by the use of the
DIM command. Remember you are not required to use the DIM
command UNLESS you plan to use more than 10 subscripts.
When you use DIM(11) you are planning on using 12 subscripts
as the DIM count starts with zero.

DD Attempt to redimension an array.

Be careful where you put the DIM statement in your program,
because if the program returns to the line in which you have
placed the DIM statement, you will get this error. Make sure
in planning your program that the initialisation process, of
which the DIM statement may be an essential part, occurs at
the beginning and the program does not regress.

DS Direct statement

Can occur because there is a direct statement in a data file,
perhaps by loading an ASCII file which has 'lost' a line
number. Files loaded off Bulletin Boards were prone to this
error.

FM Bad file mode

If you have both double and single drives you may be prone to
this error, or use a mix of single and double sided disks on
your drives. The reason is that if you use a single sided
disk in a double sided drive, the DOS reads the disk on
startup or reset and expects the same type of disk in that
drive, so when you put a double sided disk in the drive it is
reading from Sector 18 to Sector 1 and doesn't recognise that
the program continues on Sector 19 etc.
The solution is to press the RESET button.
Of course if you've got single sided drives and you're
attempting to read a double sided disk, you'll get this error
and there's nothing you can do about it!

NE File non-existent

The Computer can't find the file you want. If you've got more
than one drive you may have omitted to prefix the filename
with the drive number and a colon. or in the case of the Coco
placed these AFTER the filename.
e.g. Dragon - LOAD"2:FILENAME
Coco - LOAD"FILENAME:1
Although the numbers are different, in both cases you are
loading the file from Drive 2.
This error also occurs if you are using the COPY, KILL or
RENAME commands and omit the extension.

NF NEXT without FOR

This occurs when the command NEXT is used without a matching
FOR. Sometimes occurs through bad programming practice such
as jumping into loops. Often occurs when the NEXT commands
are reversed in nested loops.
As programs are increased in speed by NOT using the variable
with NEXT (ie NEXT X), the variable is unnecessary; the
computer knows which variable to use, even if you've
forgotten!

TF Too many open

Files that is. One of the easiest errors to fall into, when
you go from using Coco disk drives to the Dragon. The Coco
keeps track of its files differently to the Dragon reserving
buffer space etc. You dont have to keep closing Coco files,
but it is good practice to do so on the Dragon.
There are 19 fonts in the DESKTOP program and in order to
copy these to another disk, I often wrote a short little
program to copy from 1 to 19 fonts. This would grind to a
halt with this error after copying 10 fonts, if a CLOSE
command was not included.

UL Undefined line

Occurs when a GOTO or a GOSUB is used with a line number
that is not in the program.
When you are using hybrid programs which are a mix of Basic
and machine code routines, this error may be the first
indication that your program has crashed. The program is
possibly trying to jump to a line near the end of the
program, but when you list it you find you've lost the end
of your program. You can sometimes RESCUE it by using the
RENUM command and although it won't Run, you can save it and
when reloaded it will probably run.

DATA

Most mistakes occur when you type in programs from magazines
etc, through the misreading of 8 and B in machine code, or
by using an O in Hex notation instead of an 0. An the
reverse is the case in music notation using an 0 in mistake
for the O for the octave.
Programmers who use an I or an O for a variable are asking
you to fall in the trap and type a 1 or an 0. They are so
difficult to spot if you go wrong. Especially if you get an
FC error which refers to a string some lines back.

Remember Murphy's Law, "If you don't want it to happen it
probably will". I remember one program of Pam D'Arcy's that
I had on tape in the days when I first purchased a disk
drive. It was called TAPESCAN or SCANTAPE and as its name
implies, used to scan through a tape and tell you what was
on the tape and if the program was in machine code, what the
relevent addresses were. In those days, I was always
leaving a disk in the drive (a bad practice which I don't
recommend to anyone). Anyway, every time I used TAPESCAN it
did a grand job on my tape, but it wiped the disk directory
and replaced it with gobbledegook. It used to drive me mad,
but it taught me to never leave disks in the drive.

== GRAPHIC MODES of the DRAGON and COCO ==

NOTE - Modes 3 to 9 are not supported by Basic, but can be
poked and used in your programs. One such program was called
'Semigraphics 24' and was written by A C Daniel, it appeared
in Dragon User magazine August 1985.

MODE 1 Standard text screen 32 x 16 bytes (512)

MODE 2 Semigraphic 4 SET/RESET as above screen.
Same as Alphanumeric screen above and is
supported by basic. Element size 64 x 32.

MODE 3 (not supported by Basic)

Semigraphic 6 Element size 64 x 48
512 bytes - 4 colours per colour set.
SELECT with the following:-
A=PEEK(65314):POKE65314,AAND7+16+C
Where C=0 or C=8 for Colorset 0 or 1.
POKE65476,0:POKE65474,0:POKE65472,0

MODE 4 (not supported by Basic

Semigraphics 8 - Element size 64 X 64
2048 bytes - 8 colours - Border black
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65475,0:POKE65475,1:POKE65472,0

MODE 5 (not supported by Basic)

Semigraphics 12 - Element size 64 x 96
3072 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK(65314):POKE65314,(A AND 7)
POKE65477,1:POKE65474,0:POKE65472,0

MODE 6 not supported by Basic)

Semigraphics 24 - Element size 64 x 192
6144 bytes - 8 colours - Black border
SELECT with the following:-
A=PEEK65314):POKE65314,(A AND 7)
POKE65477,1:POKE65475,1:POKE65472,0

NOTE - In the Semigraphic 8 colour modes, the colours are
set with the MSB which ALWAYS has bit 7 set (1) and the rest
of the MSB (ie bits 6,5 &4) are set for the colours as
follows:
000 GREEN 001 YELLOW
010 BLUE 011 RED
100 BUFF 101 CYAN
110 MAGENTA 111 RED

MODE 7 (not supported by Basic)

64 X 64 GRAPHICS - FOUR COLOUR
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+C
Where C=0 for Colour set 0
c=8 for Colour set 1
POKE65473,1:POKE65474,0:POKE65476,0
Uses 1024 bytes. To START see end of section.

MODE 8 (not supported by Basic)

128 x 64 TWO COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+16+C
WHERE C=0 OR C=8 FOR COLOUR SETS 0 OR 1.
POKE65473,1:POKE65474,0:POKE65476,0
AGAIN USES 1024 BYTES. TO START SEE END.

MODE 9 (AGAIN NOT SUPPORTED)

128 X 64 FOUR COLOURS
Select with -
A=PEEK(65314):POKE65314,(AAND7)+128+32+C
WHERE C=0 OF C=8 FOR COLOUR SETS 0 OR 1.
POKE65472,0:POKE65475,0:POKE65476,1
Uses 2048 bytes.

MODE10 is PMODE0 - 1536 bytes - 2 colour

MODE11 is PMODE1 - 3072 bytes - 4 colour

MODE12 is PMODE2 - 3072 bytes - 2 colour

MODE13 is PMODE3 - 6144 bytes - 4 colour

MODE14 is PMODE4 - 6144 bytes - 2 colour

== BIBLIOGRAPHY ==

The Major work regarding Graphics is William Barden's COLOR
COMPUTER GRAPHICS published by TANDY (now out of print in
this country). He describes bit mapping for all the non
supported modes. Although intended for the TANDY COCO, it
also applies to the Dragon, which uses the same SAM chip.
Other books, if you can find them, are:-
ADVANCED SOUND AND GRAPHICS by Keith and Steven Brain -
published by SUNSHINE Books.
PROGRAMMING THE DRAGON for GAMES & GRAPHICS by Geoff
Phillips - published by McGRAW-HILL
INSIDE THE DRAGON by Duncan Smeed & Ian Sommerville -
published by ADDISON-WESLEY.
Chapter 7 applies.
DRAGON 32 PROGRAMMER'S REFERENCE GUIDE by John Vander Reydon
- published by MELBOURNE HOUSE.

== MEMORY MAP ==

DRAGON 32 and 64 in 32 mode

<pre> 0 - 1023 0000 - 03FF SYSTEM USE
1024 - 1535 0400 - 05FF TEXT SCREEN
1536 - 3071 0600 - 0BFF GRAPHICS: PAGE 1
3072 - 4607 0C00 - 11FF PAGE 2
4608 - 6143 1200 - 17FF PAGE 3
6144 - 7679 1800 - 1DFF PAGE 4
7680 - 9215 1E00 - 23FF PAGE 5
9216 - 10751 2400 - 29FF PAGE 6
10752 - 12287 2A00 - 2FFF PAGE 7
12288 - 13823 3000 - 35FF PAGE 8
13824 - 32767 3600 - 7FFF PROGRAM USE
32768 - 49151 8000 - BFFF BASIC ROM
49152 - 65279 C000 - FEFF CARTRIDGE USE
65280 - 65535 FF00 - FFFF INPUT/OUTPUT
</pre>

PLEASE NOTE:
With disks in use, the Disk work space occupies the first
page of graphics (1536 to 3071) and in consequence Graphics
screens are moved up one page, starting at 3072 (&H0C00) and
ending at 15359 (&H3BFF).
On start up the Dragon does a PCLEAR4 and in consequence the
memory available for program use starts at 7680, or 9216
with the DOS Controller in place.

DRAGON 64 in 64 MODE.

Same as above, except the BASIC ROM is moved from 32768
(&H8000) to 49152 (&HC000), which gives a substantial
increase in memory available for program use, but means that
disks cannot be used as the ROM overlays the Cartridge area.
Programs exist to overcome this problem however.

<pre>13824 - 49151 3600 - BFFF PROGRAM USE
49152 - 65279 C000 - FEFF BASIC ROM
65280 - 65375 FF00 - FF5F INPUT/OUTPUT
65376 - 65503 FF60 - FFDF SAM CONTROL BITS
65504 - 65535 FFE0 - FFFF MPU VECTORS</pre>

NOTE

The following pages contain details of the Dragon's memory,
both the Basic work pages and the Basic ROM. While every
effort has been made to ensure the accuracy of these
details, the Editor has had to rely on a number of sources
and it has not been possible to check them all.
Where possible details have also been given of the Tandy
Coco2 equivalent, making it possible for the conversion of
programs from American sources. In so doing you are reminded
that the Coco disk system differs greatly from Dragondos and
is closer to the cassette system in the way that it handles
data files.
One other major difference is the way that graphic binary
files are stored, they are usually 512 bytes higher in
memory than Dragon graphics.

== MEMORY MAP DETAILS ==

0 0 BREAK message flag
1 1 STRING delimiting character
2 2 Another delimiting character
3 3 General counter
4 4 Count of IF's seen looking for ELSE
5 5 DIM flag
6 6 VARIABLE type flag 0=numeric 255=string
7 7 Garbage collection flag
8 8 Subscript allowed flag
9 9 INPUT/READ flag
10 A Arithmetic use
11) B) String pointer - first free temporary
12) C)
13) D) String pointer - last used temporory
15-24 E-18 Temporary results
25/26 19/1A Start address of Basic program
27/28 1B/1C Start address of simple variables table
see D User 1/86 p38 for details of
variables.
29/30 1D/1E Start address of ARRAY table
31/32 1F/20 End of storage (last byte used by Basic)
33/34 21/22 Top of Stack. ((Stack grows down)
35/36 23/24 Top of free STRING space. By subtracting the
contents of 33/34 you get free string space
37/38 25/26 Pointer to STRING in string space
39/40 27/28 Top of RAM available to Basic
41/42 29/2A Line number used in 'CONT' command
43/44 2B/2C Temp G.P. line number store
45/46 2D/2E Pointer to statement to be executed
47/48 2F/30 Direct mode command text pointer
49/50 31/32 Current DATA statement line number
51/52 33/34 Address of next item in current data sta'nt
53/54 35/36 Address of keyboard input buffer
55/56 37/38 Pointer to VARIABLE last in use
57/58 39/3A VARPTR address of variable last in use
59/78 3B/4E Evaluation variables
65/66 41/42 High end destination address for block move
67/68 43/44 High end origin address
69/70 45/46 Low end destination address
71/72 47/48 Low end origin address
79/84 4F/54 Floating Point Accumulator: No 1
79 4F Exponent )
80/83 50/53 Mantissa ) Details of FPA
84 54 Sign )
85 55 Temporary sign of FAC
86 56 String variable length
92/97 5C/61 Floating Pt Acc No 2: details as before
98 62 Sign comparison
99 63 Extended precision byte-Coco
104/105 68/69 Current line number (65535 in direct mode)
106 6A VDU Comma field width (default 16)
107 6B VDU Last Comma field (screen width - above)
108 6C VDU Current column number (0 - 31)
109 6D VDU Line width. No of characters per line
110 6E Cassette I/O flag. Set FF on input incurring
111 6F DEVN: re text output: 0=VDU 255=tape 254=prt
112 70 Cassette EOF flag: EOF reached if non zero
113 71 Restart flag. If<>$55 - cold start on reset
114/115 72/73 Restart vector. If flag=$55 & vector points
points to a NOP then warm start else
a cold start.
116/117 74/75 Physical end of RAM
120 78 Cassette status:0=closed 1=input 2=output
121 79 I/O buffer size
122/3 7A/B Header buffer address:where f'name block is
124 7C Cassette block type:
0=f'name block 1=data block 255=EOF marker b
125 7D BLKLEN:Cass Block length:Bytes to read/write
126/7 7E/F Cassette I/O buffer address
128 80 Used internally to calculate the checksum
129 81 I/O error code 1=CRC 2=attempt load into RAM
130/2 82/4 Temp store used by COS
133 85 Last sine value
134 86 Data for Lo-res SET/RESET routine
135 87 ASCII code of last key pressed
136/7 88/89 Current VDU cursor address (ie screen pos)
138/9 8A/B G.P. (16 bit) scratch pad
140 8C Sound pitch value (frequency)
141/2 8D/E GP Countdown facility (?duration of sound)
143 8F Cursor Flash Counter
144/5 90/1 Cassette leader byte count (number of &H55s)
146 92 Min Cycle width of 1200HZ - Init=12
147 93 Min Pulse width of 1200HZ - Init=0A
148 94 Max pulse width of 1200HZ - Init=12
149/50 95/6 Dragon - Motor on delay
Coco - Serial printer Baud rate constant
HEX Msb Lsb (decimal) Baud
149 150
02EB 2 235 75
01CA 1 202 120
0173 1 115 150
00BE 0 180 300
0057 0 87 600 (default)
0028 0 41 1200
0012 0 18 2400
0006 0 6 4800
0001 0 1 9600
151/2 97/8 Keyboard Scan Delay constant: Init=&H045E
153 99 Printer Comma Field Width: Default 16
154 9A Printer Last Comma Field
155 9B Printer Line Width: Set this to width 80?
156 9C Printer Head Column:same as POS(-2) in basic
157/8 9D/E Exec Entry address
159/170 9F/AA Self modifying routine which reads next char
166/7 A6/7 Address of current sig byte - next char pntr
171/4 AB/E Used by RND command
175 AF TRON/TROFF flag: Non zero - trace on
176/7 B0/1 Address os start of USR address table
178 B2 Current foreground colour
179 B3 Current Background colour
180 B4 Temp colour in use
181 B5 Byte value for current colour: ie bits set
182 B6 Graphics PMODE number in use.
183/4 B7/8 Address of LAST byte of current graphics
185 B9 Number of bytes per line in current PMODE
186/7 BA/B Address of FIRST byte: current graphics disp
188 BC Start of graphics pages (MSB) defaults to 06
Changed to 0C by Dragondos
189/90 BD/E Current X Cursor position (not available
191/2 BF/C0 Current Y Cursor position (n.a.)
193 C1 Colour Set currently in use
194 C2 Plot/Unplot flag:0=Reset, Non-zero=Set
195/96 C3/4 Current Horizontal Pixel number
197/8 C5/6 Current Vertical Pixel number
199/200 C7/C8 Current X cursor co-ordinate
201/2 C9/CA Current Y cursor co-ordinate
203/4 CB/CC Circle command X co-ordinate
205/6 CD/CE Circle command Y co-ordinate
207/8 CF/D0 RENUMber increment value
209/10 D1/2 RENUMber Start line (original number)
211/2 D3/4 CLOADM: 2's complement load offset value
213/4 D5/6 RENUMber New Start line (new number)
215 D7 Editor line length - not user available
216/221 D8/DD Graphics use
222 DE Current octave in use (0 - 4)
223/4 DF/E0 Volume data for volume setting in PLAY
225 E1 Current note length in PLAY
226 E2 Current TEMPO for PLAY command
227/8 E3/4 Music duration count
229 E5 Music dotted note flag
230 E6 Coco - Baud rate constant
231 E7 Coco - Input timeout constant
232 E8 Current ANGLE used in DRAW routine
233 E9 Current SCALE used in DRAW routine
234 EA Disk operation code-what operation specified
235 EB Disk Drive number(1 - 4) Coco(1 - 3)
236 EC Disk read/write TRACK number
237 ED Disk read/write SECTOR number
238/9 EE/F Disk read/write Sector Buffer address
240 F0 Disk Error Status byte (Convt to DDOS code)
241 F1 Disk File Control Block number (1 - 10)
242 F2 Number of bytes in Disk buffer area
243 F3 No of bytes to transfer to/from buffer
244 F4 Number of SIDES/TRACKS for current drive
00=1 side 40 tracks 01=2 sides 40 tracks
FF=1 side 80 tracks FE=2 sides 80 tracks
The FORMAT of a disk is taken from the last
few bytes of Sector 1 of Track 20 in Drogon
DOS, on first access of disk after switch on
or RESET.
245 F5 File Read/write flag
0=read, 1=write & FF=verify
246 F6 Disk I/O in progress flag
256/8 100/2 SWI3 JUMP VECTOR - called from &HFFF2
Execution of a SWI3 instruction of &H113F
will stack Registers and jump here
259/61 103/5 SWI2 JUMP VECTOR - called from &HFFF4
Execution of a SWI2 instruction of &H103F
will stack registers and jump here
262/4 106/8 SWI1 JUMP VECTOR - called from &HFFFA -&H3F
will stack registers and jump here
265/7 109/B NMI JUMP VECTOR -non-maskable interrupt
called from &HFFFC, set to &H7ED7AE JUMPD7AE
by initialisation of disk operating system
in the Coco. Okay for Dragon?
268/70 10C/E IRQ JUMP SECTOR - Interrupt request called
from &HFFF8. Set to &H7EA9B3 to initialise
Basic, Set to &H7E894C for initialisation of
extended Basic or set to &H7ED7BC for the
initialisation of DOS in the Coco.
271/3 10F/111 FIRQ JUMP VECTOR - Fast interrupt request
called from &HFFF6, set to &H7EA0F6 by the
initialisation of Basic and causes a jump to
the Cartridge Port in the Coco.
274/6 112/4 In Coco this is EXEC of USR basic function
274/5 112/3 Timer - current value of system timer
In both Dragon and Coco (double function)
277/81 115/9 Random number seeds used in RND function
282/7 11A/F Unused in Dragon
282 11A Coco - Caps lock 1=lock 0=unlock (lower case
283/4 11B/C Coco - keyboard delay constant
285/7 11D/F Coco - Vector to 45509 (JUMP $8489)
288 120 Number of Basic commands (reserved words)
289/90 121/2 Address of list of Basic commands
291/2 123/4 Address of Command Despatch Table
293 125 Number of Basic functions
294/5 126/7 Address of list of Basic functions
296/7 128/9 Address of Function Despatch Table
298/307 12A/133 As for 288 to 297, but in Dragon refers to
Disk commands and functions, but in the Coco
to Extended Basic commands and functions.
308/317 134/13D These addresses as above re COCO disks.
308/327 134/147 DRAGON - USR Table (20 bytes 2 each USR)
This USR table is switched to 1667 to 1686,
or Hex 683 to 696 when DOS is connected and
is replaced with Disk Stub3 which acts as a
terminator.
328 148 PRINTER AUTO LF/CR Flag
329 149 Dragon - Caps Lock flag:non zero=upper case
330 14A Number of chars in end of line sequence(1-4)
331/4 14B/E End of Line Characters: Set to CR/LF/NUL/NUL
This sequence is sent to printer when a
carriage return is output.
336/45 150/9 Dragon Keyboard 'Roll-over' table
338/45 152/9 Coco Keyboard 'Roll-over' table

DRAGON/COCO KEYBOARD ROLLOVER TABLE

Response:
Address 191 223 239 247 251 253 254
Dec Hex D C D C D C D C D C D C D C
338 152 ENT ENT X 8 P 0 H X @ P 8 H 0 @
339 153 CLR CLR Y 9 Q 1 I Y A Q 8 I 1 A
340 154 BRK BRK Z : R 2 J Z B R : J 2 B
341 155 ; S 3 K C S ; K 3 C
342 156 , T 4 L D T , L 4 D
343 157 - U 5 M E U - M 5 E
344 158 . V 6 N F V . N 6 F
345 159 SPC / W 7 O SPC G W / O 7 G

RESPONSE IS 255 OR &HFF IF NO KEY IS PRESSED

346 15A Right Joystick(0) - X value
347 15B Right Joystick(1) - Y value
348 15C Left Joystick (2) - X value
349 15D Left Joystick (3) - Y value

350 to 424 15E to 1A8 RAM HOOKS (each 3 bytes)
350/2 15E/160 Device Open- called just before OPEN command
353/5 161/3 Device Number-called when a DEVN is verified
356/8 164/6 Device Initialisation- called before setting
up the Device parameters in Loctn 106 to 109
359/61 167/9 OUTPUT CHAR TO DEVN:called just before out-
putting char in A Reg to DEVN
362/4 16A/C INPUT CHAR FROM DEVN: called just before
inputting a char from DEVN into A Register
365/7 16D/F INPUT FILE: called just before inputting a
file using INPUT
368/70 170/2 OUTPUT FILE: called just before outputting
to a file using PRINT
371/3 173/5 CLOSE ALL FILES: called before all files are
closed, action only taken if Cassette open
374/6 176/8 CLOSE FILE: called before device is CLOSED
action only taken if DEVN is -1 (tape)
377/9 179/B COMMAND INTERPRETER: called before interpret
of token in A Reg as command, used by Delta
380/2 17C/E RE-REQUEST INPUT. Called before requesting
more data from keyboard- ie before ?? prompt
383/5 17F/181 CHECK KEYS. Called before keyboard scanned
for BREAK and SHIFT/@. Keyboard not scanned
if DEVN is -1.
386/8 182/4 LINE INPUT FILE. Called before Line Input is
executed on current DEVN
389/91 185/7 CLOSE FILE & COMMAND. Called before closing
an ASCII file just read in as a Basic prog'm
by CLOAD & returning to COMMAND mode.
392/4 188/A CHECK EOF. Called before checking for EOF
for current DEVN
395/7 18B/D EVALUATE EXPRESSION. (obvious)
398/400 18E/190 USER ERROR TRAP. Can be patched by the user,
that is in Basic, to trap error messages.
401/3 191/3 SYSTEM ERROR TRAP. Can be patched by the
'system', ie Basic extension ROMs to trap
errors (used by Dragondos)
404/6 194/6 RUN LINK. Called when RUN command is about
to be executed. Patched by DDOS to allow a
disk filename to be specified.
407/9 197/9 RESET BASIC MEMORY. Called from two routines
in ROM before Basic Memory vectors are
changed, ie by entering or editing lines,
running programs etc.
410/2 19A/C GET NEXT COMMAND. Called before reading in
the next Basic command to be executed while
program is running.
413/5 19D/F ASSIGN STRING VARIABLE. (obvious)
416/8 1A0/2 SCREEN ACCESS. Called before the CLS,GET and
PUT commands are executed.
419/21 1A3/5 TOKENISE LINE. Called before an ASCII line
is tokenised in internal Basic format
422/4 1A6/8 DETOKENISE LINE. Called before a Tokenised
line is converted to ASCII characters
425/464 or 1A9/1D0 STRING BUFFER AREA
465 1D1 Cassette filename length
466/73 1D2/9 Cassette filename to search for/or write out
474/728 or 1DA/2D8 CASSETTE FILE DATA BUFFER
Area of memory used to load filename block &
ASCII data blocks - if this contains a file-
name block then this can be peeked (474-488)
474/81 1DA/1E1 Cassette filename (in buffer)
482 1E2 File type: 0=token basic 1=ASCII 2=binary
483 1E3 ASCII flag: 0=binary, non-zero=ASCII files.
484 1E4 Gap flag: 1=continuous, 255(FF)=gapped files
485/6 1E5/6 Execution address of machine code file
487/8 1E7/8 Load address of ungapped machine code file
729/33 2D9/C Basic line input buffer preamble
734/984 2DD/3D8 Basic line input buffer
985/1002 3D9/EA BUFFER space
1003/20 3EB/3FC Unused
1021/2 3FD/E End of line delay - RS 232 port on D64
1023 3FF D64 RS 232 port Baud rate controller port
1024) 400) TEXT SCREEN
1535) 5FF) Default area.

The Coco Buffer areas are slightly different:
733/988 2DD/3DC 255 byte Keyboard buffer
737/827 2E1/33B 90 byte Screen buffer

The Disk Work area is from 1536 to 3071, or &H0600 to &H0BFF
Otherwise if disks are not installed these addresses are in
respect of the first of the Graphic pages, but with the DOS
installed the Graphics page 1 starts at 3072 (&H0C00).

== DRAGONDOS WORK SPACE ==

1536 0600 Start of Disk work space or Graphics Page 1
when Disk cartridge not installed
1541 0605 Countdown to Disk motor off: Off when zero
1544 0608 Auto Verify ON/OFF: 0=off else checks sector
1546 060A Current Default drive No. Used when no Drive
number is specified in the command
1549/50 060D/E Auto command line number in use
1551/2 060F/10 Auto command increment value
1553 0611 Program LOAD/RUN flag: 0=Load else Load/RUN
1555 0613 Auto command ON/OFF flag: 0=off else Auto on
1556 0614 Error command ON/OFF flag: 0=off else ERR on
1557/8 0615/6 ERROR trap line number: Basic line error rtn
1559/60 0617/8 ERL: line number of last error
1561 0619 ERR: Error code of last basic error
1562/3 061A/B Address of start of statement in error
1564/9 061C/21 Drive 1 details
1570/5 0622/7 Drive 2 details
1576/81 0628/D Drive 3 details
1582/7 062E/33 Drive 4 details
1588) 0634) Disk Buffers 1 to 4 details, 7 bytes each
1615) 064F)
1616/66 0650/82 Current Drive information
1618/9 0652/3 Start address of program loaded
1620/1 1654/5 Length of program loaded
1622/3 1656/7 Entry (EXEC) address of M/code program
1667/86 1683/96 USR Vector table: relocated from 308-327(dec
1687 to 1706) Disk Drive Parameter table
0697 to 06AA) 4 bytes per parameter - 1 for each drive
1687/90 0697/A On Line Flag: Non zero means dive on line
1691/4 069B/E Current Track, if Drive on line
1695/8 069F/A2 Head Stepping rate: This should only be
changed if slower drives are used.
1699/702
06A3/6 Disk Tracks on each drive
1703/6 06A7/A Disk Sectors per track on each drive
1707/24 06AB/BC Directory Sector status
1725/2034 File Control Blocks: 10 in all: One for each
6BD/7F2 open file: Each FCB 32 bytes long
2035/47 7F3/F Temporary variables
2048/3071 )Disk Buffers: 4 in all, each 256 bytes long
800/BFF)

3072 0C00 Start of Graphic Page 1 when disks in place
otherwise start of Graphic Page 2 for tapes.

== BASIC INTERPRETER CODES ==

32768 8000 Hardware initialisation
32771 8003 Software initialisation
32774 8006 POLCAT:Keyboard input:put into Register A
32777 8009 Cursor Blink
32780 800C CHROUT:Write character in Reg A to screen
32783 800F Writes out character in Reg A to printer
32786 8012 Joystick input:stored in addresses 346/9 dec
32789 8015 Cassette on
32792 8018 Cassette off
32795 801B Write leader to cassette (or A00C)
32798 801E Output byte from Reg A to cassette
32801 8021 CSRDON:Cassette on, prepare for reading
32804 8024 Input one byte from cassette to Register A
32807 8027 Gets one bit in from cassette into carry
32810 802A Reads in a byte from another computer
32813 802D Sends a byte to another computer
32816 8030 Select Baud rate of communications line

From here on the Coco equivalents are given in brackets and
only a few Hex addresses will be given

33604 (44102) SYSERR: Generates appropriate action for
Error code in B Reg
33649 (44147) CMDMODE: prints OK prompt & returns to the
command mode
33773 (44271) BASVECT2: complete initialisation process
after Basic program loaded
33815 (44313) NEW Basic:removes current Basic program from
memory, resets stack & clears variables
33823 (44321) BASVECT1: Sets up various necessary vectors,
once a Basic program has been loaded
33844 (44339) RESETS STACK: Resets stack to initial pos'tn
all entries are lost
33951 (44446) RUN BASIC: runs a basic program in memory,
used to AUTORUN programs
34091 851B (44539) WAIT KEY: waits for a key press, and
when key pressed puts it in A Register
34935 (45382) GET EXPR: routine will evaluate & put VARPTR
address of following expression into 82/83
34951 (45398) GET STRG: compiles a string and puts it into
free string space
35236 (45671) CKCLBRAK: as for CKCOMA, but checks for a
closed bracket
35239 (45674) CKOPBRAK: as for above, but checks for an
open bracket
35242 (45677) CKCOMA: Checks to see next significant char
in command line is a comma, and if not it
produces a SYNTAX error
35244 (45679) CKCHAR: as for CKCOMA, but checks for char
in B Register
35476 (45911) GETVAR: Get VARPTR address of the follwing
variable's name
35625 (46057) GETUSR: Returns value of the argument in the
USR function as 16 bit number in D register
35632 INTCNV: pass parameters to M/code routine
35641 GIVABF:used to pass values from M/C to Basic
35893 (46322) ASSIGN-16-BIT:assigns value in D Register to
a numeric variable
35894 (46323) ASSIGN-8-BIT:assigns value in B register to
a numeric variable
Page 34

36055 (46481) GARBAGE COLLECT: forces a controlled garbage
collection of string space
36255 (46681) DELVAR: frees space taken by a variable
36433 (46859) GET-8-BIT: returns value of the following
number in B Register
36483 (46909) GET-16-BIT: returns value of the following
number in X register
36522 (46948) LIST BASIC: lists basic program in memory to
to DEVN (device specified)
37025 90A1 (47448) PRINT CR/LE: moves cursor position
to start of a new line
37093 90E5 (47516) OUT STRING:Outputs a text string to
device number in DEVN
38266 957A (48588) PRINT NUMBER:outputs 16 bit number
in D Reg to DEVN
38798 978E RANDOM NUMBER: Generates an 8 bit random
number and puts it in location 278
39998 (34830) ASSIGN-16-BITB:alternative to 35893, assigns
value in Locs 82/83 to a variable
41194 A0EA (36038) WAIT WITH CURSOR:scans keyboard for
a keypress, flashing cursor at print pos.
43207 (38201) CLEAR GRAPHICS:clears current graphics
screen to data in B Register on entry
43304 (38298) SET COLOURS: sets up locations 180 & 181
43320 (38314) SELECT DISPLAY: Selects text or graphics
depending on Z condition code, if Z=1 text
43322 95AC (38316) RESET VDU: resets default VDU mode
43401 (38395) SET VDG MODE:sets VDG in mode given in A Reg
43421 (38415) SET VDG OFFSET: sets display offset for the
graphics mode
43428 (38422) SELECT VDG COL: selects required VDG colour
set from the data in location 193
43489 (38483) SELECT PAGE: on entry B reg contains page no
43536 (38530) SELECT COL SET: selects colour set 0 or 1,
according to data in B reg
43555 (38549) RESERVE HRG RAM: reserves RAM for graphics
and moves basic if necessary
44698 (39639) PLAY NOTE: A Reg contains ASC code of note,
other parameters should be set up
45137 (40118) DRAW:allows access to all facilities of DRAW
46004 (40999) RESET:resets whole works, as if reset button
has been pressed
46080 (41142) BOOT BASIC: restarts the Basic interpreter
as if on power up or reset
46410 B54A (41602) OUTCHAR:outputs character in A Reg
to device number in DEVN (location 111)
46687 (42029) CLOSE FILES: closes any open tape stream and
flushes buffer
46757 (42089) WRITE BASIC: writes current basic program to
cassette
46920 (42257) READ BINARY: reads in BIN file from tape
47283 (42625) FIND FILE: searches tape for matching f'name
47411 (42753) READ 1ST BLOCK:gets filename block into tape
buffer
47422 B93E (42763) BLKIN: reads a block of data into
cassette buffer
47505 (42981) WRITE 1ST BLOCK: (obvious)
47513 B999 (42996) BLKOUT: write block of data to tape
47583 (43149) SET LRG LEVEL:on entry the X Reg contains
Lo-res screen address, B Reg colour & loc184
the OR data
47623 (43189) RESET LRG PIXEL:as above but B Reg ignored,
Pixel reset to Black
Page 35

47656 (43225) CALC PIXEL POS:on entry the top of stack
must contain Lo-res vertical co-ordinate,
preceded by horizontal co-ordinate
47735 BA77 (43304) CLEAR SCREEN: clears screen to space
and 'homes' cursor
47737 BA79 (43306) CLEAR SCREEN to CHR: clears screen
to character in B Reg
47776 (43345) BEEP:sound Beep for length held in B Reg and
pitch set by location 140
47811 (43380) AUDIO OFF: disables sound:clears bit 3 65315
47813 (43382) ENABLE SOUND: enables 6 bit sound by setting
Bit 3 of 65315
47828 (43397) RESET D/A: Puts value $7E into D/A converter
address
47830 (43399) WRITE D/A: puts contents of A Reg into D/A C
47852 (43421) AUDIO ON:on entry the B Reg must be zero
48000 BB80 BOOT BASIC64K: Boots 64 mode
48053 BBB5 (41369) UPDATE CURSOR: flashes cursor
48101 BBE5 (41409) POLCAT: scans keyboard and puts the
character in A Register
48288 BCA0 (41763) CLEAR VDU LINE: clears current VDU
line from the cursor position
48299 BCAB (41738) VDU OUT: prints char in A Reg to VDU
48373 BCF5 PRINTER DIR OUT: char in A Reg sent printer
48394 BD0A PCRLF:moves print head to start of next line
48410 BD1A (41663) PRINTER OUT:Char in Reg A to printer
48449 (43426) SELECT JSK:selects joystick sources (ports -
0 - 3) from A Register
48466 BD52 (43486) READ JSKS: Updates all joystick data
locations (346/9)
48549 BDA5 (42837) BIT IN:reads a single bit(see below)
48557 BDAD (42825) BYTE IN:reads a byte into A Reg(tape
48591 (42954) MOTOR ON: tape - sets bit 3 of $FF21
48604 (42987) MOTOR OFF: tape - clears bit 3 of $FF21
48615 (42876) READ LEADER: motor on & prepares COS to read
48658 (43050) BYTE OUT: writes byte in A Reg to tape
48746 BE6A WRTLDR:turns cassette on and writes a leader

THE FOLLOWING ARE DRAGONDOS ROUTINES

49166 C00E LENFIL: Report file length
49168 C010 CLOSAL: Close all files
49176 C018 GETFRE: Get free space
49178 C01A DELETE: Delete a file
49180 C01C PROTECT/UNPROTECT a file
49182 C01E RENAME a file
49184 C020 GETDIR: Get directory entry
49406 C0FC WRITE SECTOR: Writes 256 bytes to disk
49412 C104 READ SECTOR: reads 256 bytes from disk
49509 C165 DRIVE INIT: initialises DOS hardware
49513 C169 HARDWARE I/O: low level command to hardware
50108 C3BC FORMAT DISK: in the DEFD drive
53581 D14D GET FREE SPACE: free bytes on current drive
54033 D311 CONVERT SECTOR:converts LSN(Logical sect no)
in Y Reg to Track/Sector
55868 DA3C DIR DSK: directory of disk in DEFD drive to
DEVN
56229 DBA5 BEEP: on entry B Reg should contain number
of beeps
56267 DBCB WAIT TIME:on entry X Reg should contain the
number of milliseconds to wait
56330 DC0A BOOT DSK: boots an OS off disk in DEFD drive

== INPUT/OUTPUT ROUTINES ==

These refer to DRAGONDOS.

65280 FF00 Bits 0 to 6 Keyboard row input
Bit 7 koystick comparator input
Decimal value 255/127 if no fire but pressed
Dec value 254 or 126 if right joystick
button pressed
Dec value 253 or 125 if left joystick fire
button pressed
65282 FF02 Bits 0 to 7 keyboard column output
65312 FF20 Bit 0 - cassette data input
1 - RS232 data output
2/7 - 6 bit D/A(.25 to 4.75 volts out)
65313 FF21 Bit 0 - control of CD
0=FIRQ to CPU disabled, 1=enabled
Bit 1 - RS 232 status input
0=set flag falling edge CD, 1=rising edge
Bit 2 - normal Data Direction Register addsd
0=change FF20 to DDR
Bit 3 - Cass Motor control, 0=off, 1=on
4 - always 1
5 - always 1
6 - not used
7 - CD interrupt flag
65314 FF22 Bit 0 - RS 232 data input
1 - single bit cound output
2 - RAM size input
3 - VDG Control Output CSS(color set ct)
4 - VDG Control Output GM0&NOT(INT)/EXT
5 - VDG Cont Output GM1
6 - VDG Cont Output GM2
7 - VDG Cont Output NOT(A)/G
65315 FF23 (Coco) POKE 54 to disable auto exec of cartr
POKE 55 to enable auto execute of cartridge
Not certain re above for Dragon
Bit 0 - control of cartridge
0=FIRQ to CPU disabled, 1= enabled
Bit 1 - Interrupt input
0=sets flag on falling edge of cartridge
1=sets flag on rising edge of cartridge
Bit 2 - Normally 1, 0=changes FF22 to DDReg
3 - 6 bit sound enable
4 - always 1
5 - always 1
6 - not used
7 - Cartridge Interrupt Flag

== SAM CONTROL BITS ==

65472/7 FFC0/5 VDG Control Registers for 6883 SAM
Contains 3 pairs of addresses (V0-V2), and
poking any value to EVEN addresses sets Bit
Off(0) in VDG circuitry. Poking value to ODD
addresses set Bit ON(1) in 6847 VDG circuit
65472/3 FFC0/1 Control of Bit 0 (V0)
65474/5 FFC2/3 1 (V1)
65476/7 FFC4/5 2 (V2)
65478/91 Page Select Register contains 7 pairs of
FFC6/D3 (F0-F6) control Display Start address (Bin)
Address os upper left most display element=
0000+1/2*OFFSET. Poking any value to even
addresses sets Bit OFF (0) in Page select.
Poking any value to ODD addresses sets Bit
ON(1) in Page Select Circuitry.
Also BASEPAGE is set by converting binary
value of F (Bits F0 to F6) to decimal and
multiplying this decimal number by 512.
65478/9 FFC6/7 Control of Bit 0 (F0)
65480/1 FFC8/9 1 (F1)
65482/3 FFCA/B 2 (F2)
65484/5 FFCC/D 3 (F3)
65486/7 FFCE/F 4 (F4)
65488/9 FFD0/1 5 (F5)
65490/1 FFD2/3 6 (F6)

65492/3 FFD4/5 Page #1 P1 control of Bit 7: (F7) 0=Normal
65494/7 FFD6/9 Clock Speed (R0-R1) Poking any value to even
addresses sets Bit OFF (0). Poking any value
to ODD addresses sets bit ON (1).
65494/5 FFD6/7 Control of Bit R0
65496/7 FFD8/9 Control of Bit R1
R0=0, R1=0 (slow mode defa

== MPU VECTORS ==

<pre>
65522/3 FFF2/3 SWI 3 Vector mapped to 49138/9 BFF2/3
65524/5 FFF4/5 SWI 2 vector 49140/1 BFF4/5
65526/7 FFF6/7 FIRQ vector 49142/3 BFF6/7
65528/9 FFF8/9 IRQ vector 49144/5 BFF8/9
65530/1 FFFA/B SWI 1 vector 49146/7 BFFA/B
65532/3 FFFC/D NMI vector 49148/9 BFFC/D
65534/5 FFFE/F RESET vector 49150/1 BFFE/F
</pre>

== ERROR MESSAGES AND CODES ==

0 NF NEXT without FOR
2 SN Syntax error
4 RG RETURN without GOSUB
6 OD Out of Data in READ
8 FC Illegal Function call
10 OV Overflow
12 OM Out of Memory
14 UL Undefined Line
16 BS Bad subscript
18 DD Redimension array
20 /0 Division by Zero
22 ID Illegal Direct Statement
24 TM Type mismatch
26 OS Out of String space
28 LS String too long
30 ST String too complex
32 CN Can't continue
34 UF
36 FD Faulty data
38 AO File already open
40 DN Drive number
42 IO Input/Output error
44 FM Wrong file mode
46 NO File not open
48 IE Input past EOF (ER on the Coco)
50 DS Direct statement
128 * NR Not ready
130 * SK Seek
132 WP Write protect
134 * RT Record Type
136 * RF Record not found
138 * CC Cyclic redundancy
140 * LD Lost data
142 * BT Boot error
144 * IV Invalid Directory
146 * FD Directory full
148 DF Disk full
150 FS File Spec
152 * PT Protection on
154 * PE READ past EOF
156 * FF File not found
158 * FE File exists (AE on the Coco)
160 NE Non-existent
162 * TF Too many open
164 * PR Parameter error
* * These error messages are not on the Coco,
but the following are and are not on the Dragon.
BR Bad record number (in data)
FN Bad file name
FO Field overflow re data files
OB Out of Buffer space
SE Set to non-fielded string (data)
VF Verification error

[[Category:Documentation]] [[Category:Software]] [[Category:Development]]

System Software

2016-05-07T20:50:40Z

Tormod: links to OS-9_System

== Dragon Data ==

[[Dragon DOS]]

[[OS-9_System|OS-9 Level 1]]

[[OS-9_System|OS-9 Level 2]]

== Compusense ==

[[FLEX]]

== Premier Micro Systems ==

[[Delta DOS]]

== Eurohard ==

[[OS-9_System|OS-9 Level 1 V2.0]]

[[Category:Software]]

== The NitrOS-9 project ==

[[NitrOS-9]] Level 1

NitrOS-9

2016-05-07T20:47:33Z

Tormod:

NitrOS-9 is a multi-task operating system for the Dragon and CoCo computers. It was originally based on OS-9 from Microware as an optimized version for the 6309 microprocessor. Over time it turned into a open-source project and is still under development. NitrOS-9 Level 1 is similar to OS-9 Level 1 and can run on the Dragon 64. It can actually boot on a Dragon 32 as well, but with very little RAM left to do anything useful. NitrOS-9 Level 2 is similar to OS-9 Level 2 and requires the GIME memory management unit (MMU) and extra memory of the CoCo3.

NitrOS-9 has support for the Dragon Data disk controller (thanks to Phill) and for [[DriveWire]].

Visit the [http://www.nitros9.org NitrOS-9 project] for more information.

[[Category:Software]][[Category:System Software]][[Category:OS-9]]

Programador de EPROM (Resistor magazine)

2016-05-07T20:45:24Z

Tormod: missing gallery end tag

An EPROM programmer cartridge sold as kit through the Spanish electronics magazine ''Resistor''.

== Pictures ==

<gallery>
Image:Resistor_EPROM_Programmer_PCB_Top.jpg|PCB Top
Image:Resistor_EPROM_Programmer_PCB_Bottom.jpg|PCB Bottom
</gallery>

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]]

UDW SD-card DriveWire microserver

2016-05-07T20:39:23Z

Tormod: /* uDW (by Tormod) */ linkify

= uDW (by Tormod) =

The ''uDW DriveWire microserver'' is a standalone, SD card based mass-storage solution for the Dragon. It plugs into the printer port (instead of a [[Dragon_32/64_Drivewire_Adapter|DriveWire adapter]]) and contains an embedded [[DriveWire]] server. Programs and files are stored on a micro SD card and are accessed the same way as if they were on a PC-based DriveWire server.

* Dimensions 10 x 5 x 3 cm
* Compatible with all DriveWire software ([[DWLOAD]], HDB-DOS, [[NitrOS-9]], ...)
* Connects to printer port via IDC flat cable
* Powered by the Dragon
* Uses standard micro-SD cards (FAT formatted)
* Built-in real time clock
* Firmware upgradeable over USB

[[File:udw.jpg]]

http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=6&t=4981

[[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Drivewire]]

Dweebs

2016-05-07T20:33:44Z

Tormod: /* DOS */ linkify NitrOS-9

== What are dweebs? ==

They're '[[DWLOAD]] Extensible Execution Blocks', a method for extending the functionality of [[DWLOAD]], a tool used to access [[DriveWire]].

== How do they work? ==

The DWLOAD client is relatively simple, due to the space constraints in the ROM. The dweeb is a mechanism to dynamically extend the functionality of DWLOAD. The dweeb is loaded from the server like any other program, but accesses the I/O routines of DWLOAD. It also reads its command parameters from the DWLOAD command line.

The best example is the "SAVE" dweeb. There is not enough room in the ROM to include support for saving files over DriveWire. However, this functionality can be loaded on demand. DLOAD"SAVE""MYFILE.BAS" saves a BASIC program to the DriveWire server. The SAVE functionality is only temporarily loaded into RAM and used during this invocation.

Since a dweeb uses the I/O routines of the calling DWLOAD, it is independent of the real transport being used, which makes development with for instance the Becker interface in XRoar very convenient.

Examples:

DLOAD"VLOAD""MYIMAGE.VDK""MYFILE.BAS"
DLOAD"DOS"
DLOAD"LROM""GAME.ROM"

== How do you install them? ==

Normally, dweebs live in the top directory of your Drivewire server - simply unzip the archive and put the files in there. However, you can create subdirectories in your Drivewire directory, for example:

DLOAD"DWEEB/DATE"
DLOAD"VDK/VDIR""DISK.VDK"

You can also use variables with your dweebs, for example:

D$="DWEEB/DATE"
DLOADD$

== The Dweeb Directory ==

This is a list of the known Dweebs, extracted from posts on the forum. Please feel free to add any others to this list.
''Note:'' CocoSDC users will use DWLOAD instead of DLOAD for all these examples.

=== File Manipulation Dweebs ===

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&p=12300&hilit=LDAF#p12300 LDAF] ====
Allows the user to load an ASCII basic file.
DLOAD"LDAF""HELLO.BAS"
''Note:'' See [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=LDAF&start=50#p14791 this post]] for the latest version. Also note that LDA (and the original version of LDAF) '''only''' work with DOS files.

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968#p12106 LROM] ====
Allows the user to load (and run) any ROM file.
DLOAD"LROM""ROMName (no need to put the .ROM extension)

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=CAS&start=50#p13706 CAS] ====
A simple CAS parser to load CAS files directly from the DriveWire server.
DLOAD"CAS""MYFILE.CAS"

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 SAVE/RESAVE] ====
Save a basic program to the DriveWire server. ''Note:'' The commonly used Java based DW4 server currently doesn't support saving to a new file. In this case, use RESAVE to save over the top of an existing, possibly empty, file.
DLOAD"SAVE""MYFILE.BAS"
DLOAD"RESAVE""MYFILE.BAS"

=== Disk Manipulation Dweebs ===

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=FLO2V#p12107 FLO2V] ====
Allows copying a floppy from the default Dragon drive to a new VDK file in the PC Windows file system so you can save a backup of the disk and use it on XRoar as well.
DLOAD"FLO2V""VDKName.VDK"
''Note:'' See [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=VLOAD&start=40#p13154 this post]] for the latest version

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=V2FLO#p12107 V2FLO] ====
Allows copying an VDK to a floppy on the default Dragon drive to restore a previous backup or simply to transfer a XRoar disk to the real Dragon drives.
DLOAD"V2FLO""VDKName.VDK"
''Note:'' See [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=VLOAD&start=40#p13154 this post]] for the latest version

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=VDIR#p12108 VDIR] ====
Produces a directory list of the disk image.
DLOAD"VDIR""DiskName"
''Note:'' See [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=VDIR&start=30#p13033 this post] for the latest version

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=VLOAD#p12110 VLOAD] ====
Allows the user to load and run/execute any program contained in any VDK image
DLOAD"VLOAD""DiskName""FileName.Ext"
''Note:'' Also see [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=VLOAD&start=30#p13037 this post] for the latest version.

=== Drivewire and other Dweebs ===

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DATE] ====
Displays date and time from the DW4 server
DLOAD"DATE"

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968&hilit=DW&start=10#p12164 DW] ====
Sends requests to the DriveWire server.
DLOAD"DW""DW SERVER STATUS"

==== [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DOS] ====
Boot from disk 0 on DW4 server (for launching [[NitrOS-9]])
DLOAD"DOS"

DriveWire

2016-05-07T20:33:00Z

Tormod: /* DriveWire software */ linkify NitrOS-9

== Overview ==

DriveWire is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like the [[uDW SD-card DriveWire microserver|uDW]] can be used.

== DriveWire software ==

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and [[NitrOS-9]] have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive. See [[Drivewire for dummies]] for how to use HDB-DOS and DriveWire.

For Dragon there is also [[DWLOAD]] - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DriveWire adapters ==

On the Dragon you will need an adapter to convert the printer port signals to a compatible serial port (or USB virtual serial port).

See [[Dragon_32/64_Drivewire_Adapter]].

== DriveWire server software ==

The Drivewire4 (DW4) server is a Java application and can be downloaded here: https://sites.google.com/site/drivewire4/download

A lightweight alternative is "DriveWire Lite": A reimplementation in C of the server side of the DriveWire 3 protocol: http://sourceforge.net/projects/dwlite/

There is also an open-source DriveWire server written in Python: https://github.com/6809/DwLoadServer

== Drivewire4 (DW4) server usage ==

Just choose CoCo2 in the DriveWire4 server "Simple Config Wizard".
Keep all the default selections.

If you would like to use the server under Windows without installing the JRE, use this batch file for startup:
<pre>
SET JDK=%~dp0\jre
SET JAVA_EXE=%JDK%\bin\java.exe
"%JAVA_EXE%" -XX:+UseConcMarkSweepGC -jar DW4UI.jar --backup &
pause
</pre>
Download a JRE and put it into DriveWire directory together with this batch file.

== Links ==

* [https://sourceforge.net/p/drivewireserver/wiki/DriveWire_Specification/ DriveWire specification]

[[Category:Documentation]] [[Category:Drivewire]]

Repository

2016-05-07T20:32:15Z

Tormod: /* linkify NitrOS-9 */

There are many Software projects around 6809, Dragon and CoCo ...

Here a link collection of theses:

=== ToolShed ===

ToolShed is a package of utilities to perform cross-development from Windows, Linux or Mac OS X computers to the Tandy Color Computer and Dragon microcomputers. Tools are included to read/write both OS-9 RBF disk images and CoCo Disk BASIC disk images, generate cassette WAV files and more.

* Webpage: http://toolshed.sourceforge.net/
* Project page: http://sourceforge.net/projects/toolshed/
* Sourcecode repo: http://sourceforge.net/p/toolshed/code/

=== LWTOOLS ===

LWTOOLS is a set of cross-development tools for the Motorola 6809 and Hitachi 6309 microprocessors. It supports assembling to raw binaries, CoCo LOADM binaries, and a proprietary object file format for later linking. It also supports macros and file inclusion among other things.

* Project page / Sourcecode: http://lwtools.projects.l-w.ca/

=== M6809 computer tools ===

Stuff for the M6809-based Dragon and similar computers.

* https://gitorious.org/m6809-computer-tools

==== conv-tools ====
Various conversion tools for e.g. cassette and disk binary formats.
* https://gitorious.org/m6809-computer-tools/conv-tools

==== dload-dragon ====
Patched DLOAD command for Dragon 32. Uses HDB-DOS DriveWire routines to talk serial on the Dragon printer port.
* https://gitorious.org/m6809-computer-tools/dload-dragon

==== dload-server ====
A server for the DLOAD protocol, to be run on the host computer. Originally written by Burt Mitchell and ported to UNIX by Bryan Clingman.
* https://gitorious.org/m6809-computer-tools/dload-server

=== m6809 ===
Motorola 6809 dev tools: Linux packages '''xroar''', '''lwtools''', '''toolshed'''
* https://launchpad.net/~tormodvolden/+archive/ubuntu/m6809

=== '6809' GitHub organization ===
Stuff around 6809 CPU and homecomputers like Dragon 32/64, CoCo...
* https://github.com/6809/

==== DwLoadServer ====
DWLOAD server implemented in Python
* https://github.com/6809/DwLoadServer

==== dragonlib ====
Python library around 6809 computers like Dragon 32/64, CoCo...
* https://github.com/6809/dragonlib

==== sbc09 ====
sbc09 stands for Lennart Benschop 6809 Single Board Computer.
It contains a assembler and simulator for the Motorola M6809 processor.
* https://github.com/6809/sbc09

==== rom-info ====
Collected Informations/Comments for 6809 ROM Images like Dragon 32 / 64 etc...
* https://github.com/6809/rom-info

=== NitrOS-9 ===
[[NitrOS-9]] is an open-source OS-9 variant for Dragon and Tandy CoCo
* Webpage: http://www.nitros9.org/
* Project page: http://sourceforge.net/projects/nitros9/
* Sourcecode repo: http://sourceforge.net/p/nitros9/code/

=== FUZIX ===
A new UNIX-like operating system for 8-bit computers, including Dragon and Tandy CoCo
* https://github.com/EtchedPixels/FUZIX

Missing links? Just edit this page and insert it ;)

[[Category:Software]] [[Category:6809]]

DWLOAD

2016-05-07T20:31:21Z

Tormod: linkify NitrOS-9

== DriveWire overview ==

[[DriveWire]] is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like the [[uDW SD-card DriveWire microserver|uDW microserver]] can be used.

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and [[NitrOS-9]] have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive.

For Dragon there is also DWLOAD - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DWLOAD concept ==

DWLOAD is designed to be so small that it fits into unused parts of the Dragon BASIC ROM. Nonetheless, it allows you to simply download and run files from the DriveWire server from within BASIC without any resident use of memory. DWLOAD can be enhanced by "DriveWire Executable Extension Blocks" (dweebs) which are small program loaded from the server to provide further DriveWire capabilities on demand. Some examples are "VLOAD" to load files from VDK images residing on the DriveWire server, "LROM" to load a ROM image into high RAM, and "DOS" to boot NitrOS-9 over DriveWire.

DWLOAD can also be used together with HDB-DOS or Dragon DOS. You can for instance load files from the PC (plain files or from inside VDK images) and save them on your Dragon DOS floppy drive. Or load files from your Dragon DOS floppy drive and save them on the PC (currently only BASIC files supported via the "SAVE" dweeb).

== Requirements ==

In addition to your Dragon 32 or Dragon 64 or compatible home computer you will need either

DriveWire adapter + PC running DriveWire server (DW4)

or

uDW microserver

Of course, on the Dragon you will need DriveWire software. If you have the DWLOAD EPROM you are all set and can load everything (also HDB-DOS or NitrOS-9) via DriveWire. Otherwise, software (including a DWLOAD program) can be loaded from disk or cassette tape to get started.

== Using DWLOAD ==

DWLOAD is a small DriveWire client for BASIC which works without needing a DOS. It loads files as-is from the DriveWire server, that is, not using disk images like HDB-DOS or NitrOS-9 does.

Simply put: Just drop the files in your DriveWire4 server folder, and access them from the Dragon using DWLOAD.

The files can be Dragon DOS binary or BASIC files, or DECB binaries.

The DWLOAD client can be loaded from tape or disk or, most conveniently, embedded into the BASIC ROM, like the DWLOAD EPROM.

If you have the DWLOAD EPROM, use the "DLOAD" command to load files. Examples:

DLOAD"MYFILE.BAS"
to load and run the file "MYFILE.BAS" from the DriveWire server. To only load the program, use "DLOADN":
DLOADN"BROKEN.BAS"

Note that the filename ending is not significant, since the DWLOAD deduces the file type from its content.

== DWLOAD Extensible Execution Blocks (dweeb) ==

The DWLOAD client is relatively simple, due to the space constraints in the ROM. The dweeb is a mechanism to dynamically extend the functionality of DWLOAD. The dweeb is loaded from the server like any other program, but accesses the I/O routines of DWLOAD. It also reads its command parameters from the DWLOAD command line.

More information, including a directory of available dweebs, can be found on the [[Dweebs]] wiki page.

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DWLOAD forum thread]

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968 dweebs forum thread]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Software]][[Category:Drivewire]]

System Software

2016-05-07T20:28:55Z

Tormod: add NitrOS-9

== Dragon Data ==

[[Dragon DOS]]

[[OS-9 Level 1]]

[[OS-9 Level 2]]

== Compusense ==

[[FLEX]]

== Premier Micro Systems ==

[[Delta DOS]]

== Eurohard ==

[[OS-9 Level 1 V2.0]]

[[Category:Software]]

== The NitrOS-9 project ==

[[NitrOS-9]] Level 1

NitrOS-9

2016-05-07T20:27:04Z

Tormod: add categories

NitrOS-9

2016-05-07T20:25:52Z

Tormod: Created page with "NitrOS-9 is a multi-task operating system for the Dragon and CoCo computers. It was originally based on OS-9 from Microware as an optimized version for the 6309 microprocessor..."

Dweebs

2016-05-04T21:47:19Z

Tormod: /* SAVE/RESAVE */

DriveWire

2016-05-04T21:44:25Z

Tormod: link to spec + minor fixups

== Overview ==

DriveWire is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like the [[uDW SD-card DriveWire microserver|uDW]] can be used.

== DriveWire software ==

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive. See [[Drivewire for dummies]] for how to use HDB-DOS and DriveWire.

For Dragon there is also [[DWLOAD]] - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DriveWire adapters ==

On the Dragon you will need an adapter to convert the printer port signals to a compatible serial port (or USB virtual serial port).

See [[Dragon_32/64_Drivewire_Adapter]].

== DriveWire server software ==

The Drivewire4 (DW4) server is a Java application and can be downloaded here: https://sites.google.com/site/drivewire4/download

A lightweight alternative is "DriveWire Lite": A reimplementation in C of the server side of the DriveWire 3 protocol: http://sourceforge.net/projects/dwlite/

There is also an open-source DriveWire server written in Python: https://github.com/6809/DwLoadServer

== Drivewire4 (DW4) server usage ==

Just choose CoCo2 in the DriveWire4 server "Simple Config Wizard".
Keep all the default selections.

If you would like to use the server under Windows without installing the JRE, use this batch file for startup:
<pre>
SET JDK=%~dp0\jre
SET JAVA_EXE=%JDK%\bin\java.exe
"%JAVA_EXE%" -XX:+UseConcMarkSweepGC -jar DW4UI.jar --backup &
pause
</pre>
Download a JRE and put it into DriveWire directory together with this batch file.

== Links ==

* [https://sourceforge.net/p/drivewireserver/wiki/DriveWire_Specification/ DriveWire specification]

[[Category:Documentation]] [[Category:Drivewire]]

Dragon 32/64 Drivewire Adapter

2015-08-28T22:27:37Z

Tormod: explain what adapter it is and how it works

[[File:Drivewire.jpg]]‎

See also [[DriveWire]] and [[Drivewire_for_dummies]]

== Overview ==

[[DriveWire]] on Dragon uses pins on the printer port to communicate with an external DriveWire server. To convert the signal from the printer port (driven by bit-banger routines in software) into a RS232-compatible serial line, a signal inverter and level converters are needed.

The DriveWire adapter presented on this page is made by Tormod and combines an inverting circuit and a USB interface to provide a solution that plugs directly to the Dragon printer port on one end and a normal USB port in the other end.

Note that the specialized, standalone [[uDW SD-card DriveWire microserver|uDW]] DriveWire server has input circuitry adapted to the Dragon printer port and can therefore be plugged in directly without any adapter.

== Hardware ==

The built-in serial UART is the CP2102 from Silicon Labs.

== Windows ==

Windows driver can be downloaded from the chip manufacturer: http://www.silabs.com/products/mcu/pages/usbtouartbridgevcpdrivers.aspx

== Linux ==

In most cases, you simply need to run "sudo adduser $USER dialout". Read on for more details.

Some helpful commands:
<pre>
~ $ sudo lsusb | grep UART
Bus 001 Device 002: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light

$ dmesg | grep -ie cp210*
[17479.466698] usb 1-1: Product: CP2102 USB to UART Bridge Controller
[17479.548508] usbcore: registered new interface driver cp210x
[17479.548520] usbserial: USB Serial support registered for cp210x
[17479.548535] cp210x 1-1:1.0: cp210x converter detected
[17480.428168] usb 1-1: cp210x converter now attached to ttyUSB0
</pre>

Look at the last line, to see that the adapter is assigned to '''ttyUSB0'''. Check which groups have access to it:

<pre>
$ ls -l /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 0 Nov 11 13:15 /dev/ttyUSB0
</pre>
In this case you should assure that your user is in the user group '''dialout''', e.g.:
<pre>
$ groups # Display the user groups for the current user
user_foo : user_foo adm tty dialout fax cdrom floppy tape sudo audio dip video plugdev netdev fuse lpadmin scanner
</pre>
Is the group is not listed, add your user to the group, e.g:
<pre>
sudo adduser $USER dialout
</pre>

You will have to logout and relogin after this command!

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=781 DIY instructions]
* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=6&t=4270 buy a tormod's Drivewire Adapter]
* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=6&t=4854 buy a tormod's Drivewire deluxe cased adapters]
* [[DWLOAD]]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Drivewire]]

Repository

2015-08-23T10:58:23Z

Tormod: add NitrOS-9 and FUZIX

There are many Software projects around 6809, Dragon and CoCo ...

Here a link collection of theses:

=== ToolShed ===

ToolShed is a package of utilities to perform cross-development from Windows, Linux or Mac OS X computers to the Tandy Color Computer and Dragon microcomputers. Tools are included to read/write both OS-9 RBF disk images and CoCo Disk BASIC disk images, generate cassette WAV files and more.

* Webpage: http://toolshed.sourceforge.net/
* Project page: http://sourceforge.net/projects/toolshed/
* Sourcecode repo: http://sourceforge.net/p/toolshed/code/

=== LWTOOLS ===

LWTOOLS is a set of cross-development tools for the Motorola 6809 and Hitachi 6309 microprocessors. It supports assembling to raw binaries, CoCo LOADM binaries, and a proprietary object file format for later linking. It also supports macros and file inclusion among other things.

* Project page / Sourcecode: http://lwtools.projects.l-w.ca/

=== M6809 computer tools ===

Stuff for the M6809-based Dragon and similar computers.

* https://gitorious.org/m6809-computer-tools

==== conv-tools ====
Various conversion tools for e.g. cassette and disk binary formats.
* https://gitorious.org/m6809-computer-tools/conv-tools

==== dload-dragon ====
Patched DLOAD command for Dragon 32. Uses HDB-DOS DriveWire routines to talk serial on the Dragon printer port.
* https://gitorious.org/m6809-computer-tools/dload-dragon

==== dload-server ====
A server for the DLOAD protocol, to be run on the host computer. Originally written by Burt Mitchell and ported to UNIX by Bryan Clingman.
* https://gitorious.org/m6809-computer-tools/dload-server

=== m6809 ===
Motorola 6809 dev tools: Linux packages '''xroar''', '''lwtools''', '''toolshed'''
* https://launchpad.net/~tormodvolden/+archive/ubuntu/m6809

=== '6809' GitHub organization ===
Stuff around 6809 CPU and homecomputers like Dragon 32/64, CoCo...
* https://github.com/6809/

==== DwLoadServer ====
DWLOAD server implemented in Python
* https://github.com/6809/DwLoadServer

==== dragonlib ====
Python library around 6809 computers like Dragon 32/64, CoCo...
* https://github.com/6809/dragonlib

==== sbc09 ====
sbc09 stands for Lennart Benschop 6809 Single Board Computer.
It contains a assembler and simulator for the Motorola M6809 processor.
* https://github.com/6809/sbc09

==== rom-info ====
Collected Informations/Comments for 6809 ROM Images like Dragon 32 / 64 etc...
* https://github.com/6809/rom-info

=== NitrOS-9 ===
An open-source OS-9 variant for Dragon and Tandy CoCo
* Webpage: http://www.nitros9.org/
* Project page: http://sourceforge.net/projects/nitros9/
* Sourcecode repo: http://sourceforge.net/p/nitros9/code/

=== FUZIX ===
A new UNIX-like operating system for 8-bit computers, including Dragon and Tandy CoCo
* https://github.com/EtchedPixels/FUZIX

Missing links? Just edit this page and insert it ;)

[[Category:Software]] [[Category:6809]]

DWLOAD

2015-08-22T20:33:33Z

Tormod: /* DriveWire overview */ link to uDW

== DriveWire overview ==

[[DriveWire]] is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like the [[uDW SD-card DriveWire microserver|uDW microserver]] can be used.

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive.

For Dragon there is also DWLOAD - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DWLOAD concept ==

DWLOAD is designed to be so small that it fits into unused parts of the Dragon BASIC ROM. Nonetheless, it allows you to simply download and run files from the DriveWire server from within BASIC without any resident use of memory. DWLOAD can be enhanced by "DriveWire Executable Extension Blocks" (dweebs) which are small program loaded from the server to provide further DriveWire capabilities on demand. Some examples are "VLOAD" to load files from VDK images residing on the DriveWire server, "LROM" to load a ROM image into high RAM, and "DOS" to boot NitrOS-9 over DriveWire.

DWLOAD can also be used together with HDB-DOS or Dragon DOS. You can for instance load files from the PC (plain files or from inside VDK images) and save them on your Dragon DOS floppy drive. Or load files from your Dragon DOS floppy drive and save them on the PC (currently only BASIC files supported via the "SAVE" dweeb).

== Requirements ==

In addition to your Dragon 32 or Dragon 64 or compatible home computer you will need either

DriveWire adapter + PC running DriveWire server (DW4)

or

uDW microserver

Of course, on the Dragon you will need DriveWire software. If you have the DWLOAD EPROM you are all set and can load everything (also HDB-DOS or NitrOS-9) via DriveWire. Otherwise, software (including a DWLOAD program) can be loaded from disk or cassette tape to get started.

== Using DWLOAD ==

DWLOAD is a small DriveWire client for BASIC which works without needing a DOS. It loads files as-is from the DriveWire server, that is, not using disk images like HDB-DOS or NitrOS-9 does.

Simply put: Just drop the files in your DriveWire4 server folder, and access them from the Dragon using DWLOAD.

The files can be Dragon DOS binary or BASIC files, or DECB binaries.

The DWLOAD client can be loaded from tape or disk or, most conveniently, embedded into the BASIC ROM, like the DWLOAD EPROM.

If you have the DWLOAD EPROM, use the "DLOAD" command to load files. Examples:

DLOAD"MYFILE.BAS"
to load and run the file "MYFILE.BAS" from the DriveWire server. To only load the program, use "DLOADN":
DLOADN"BROKEN.BAS"

Note that the filename ending is not significant, since the DWLOAD deduces the file type from its content.

== DWLOAD Extensible Execution Blocks (dweeb) ==

The DWLOAD client is relatively simple, due to the space constraints in the ROM. The dweeb is a mechanism to dynamically extend the functionality of DWLOAD. The dweeb is loaded from the server like any other program, but accesses the I/O routines of DWLOAD. It also reads its command parameters from the DWLOAD command line.

The best example is the "SAVE" dweeb. There is not enough room in the ROM to include support for saving files over DriveWire. However, this functionality can be loaded on demand. DLOAD"SAVE""MYFILE.BAS" saves a BASIC program to the DriveWire server. The SAVE functionality is only temporarily loaded into RAM and used during this invocation.

Another typical dweeb is "DOS" for booting an operating system (NitrOS-9), similar to the DOS command in HDB-DOS or the DWDOS program.

Pere has also created some dweebs for accessing VDK disk images on the DriveWire server, this is very useful for accessing Dragon DOS program collections without using a disk drive or DOS.

Since a dweeb uses the I/O routines of the calling DWLOAD, it is independent of the real transport being used, which makes development with for instance the Becker interface in XRoar very convenient.

Examples:

DLOAD"SAVE""MYFILE.BAS"

DLOAD"VLOAD""MYIMAGE.VDK""MYFILE.BAS"

DLOAD"DOS"

DLOAD"LROM""GAME.ROM"

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DWLOAD forum thread]

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968 dweebs forum thread]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Software]][[Category:Drivewire]]

DriveWire

2015-08-22T20:30:34Z

Tormod: /* Overview */ add uDW link

== Overview ==

DriveWire is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like the [[uDW SD-card DriveWire microserver|uDW]] can be used.

== DriveWire software ==

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive. See [[Drivewire for dummies]] for how to use HDB-DOS and DriveWire.

For Dragon there is also [[DWLOAD]] - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DriveWire adapters ==

On the Dragon you will need an adapter to convert the printer port signals to a compatible serial port (or USB virtual serial port).

See [[Dragon_32/64_Drivewire_Adapter]].

== DriveWire servers ==

The Drivewire4 server is a Java application and can be downloaded here: https://sites.google.com/site/drivewire4/download

There exist also "DriveWire Lite": a reimplementation in C of the server side of the DriveWire 3 protocol: http://sourceforge.net/projects/dwlite/

There is also a OpenSource DriveWire Server written in Python: https://github.com/6809/DwLoadServer

== Drivewire4 (DW4) server usage ==

Just choose CoCo2 in the DriveWire4 server "Simple Config Wizard".
Keep all the default selections.

If you would like to use the server under Windows without installing the JRE, use this batch file for startup:
<pre>
SET JDK=%~dp0\jre
SET JAVA_EXE=%JDK%\bin\java.exe
"%JAVA_EXE%" -XX:+UseConcMarkSweepGC -jar DW4UI.jar --backup &
pause
</pre>
Download a JRE and put it into DriveWire directory together with this batch file.

[[Category:Documentation]] [[Category:Drivewire]]

UDW SD-card DriveWire microserver

2015-08-22T20:26:19Z

Tormod: /* uDW (by Tormod) */

= uDW (by Tormod) =

The uDW DriveWire microserver is a standalone, SD card based mass-storage solution for the Dragon. It plugs into the printer port (instead of a DriveWire adapter) and contains an embedded DriveWire server. Programs and files are stored on a micro SD card and are accessed the same way as if they were on a PC-based DriveWire server.

* Dimensions 10 x 5 x 3 cm
* Compatible with all DriveWire software (DWLOAD, HDB-DOS, NitrOS-9, ...)
* Connects to printer port via IDC flat cable
* Powered by the Dragon
* Uses standard micro-SD cards (FAT formatted)
* Built-in real time clock
* Firmware upgradeable over USB

[[File:udw.jpg]]

http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=6&t=4981

[[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Drivewire]]

DIY Projects

2015-08-22T20:24:54Z

Tormod: /* Cartridges & Expansions */ added uDW

The Dragon series of computers offers programming models and a cartridge expansion connector that are ideally suited to hardware hackers and hobbyist experimenters. Below, you can find a selection of projects that have been created by members of the Dragon community.

Click the item to learn more about it, buy one or download schematics and associated software (where applicable).

== Adapters & Cables ==
* [[Replacement power supply unit]]
* [[Dragon32/iPhone Bi-Directional Data Cable (Rink)]]
* [[Dragon 32/64 Drivewire Adapter]]
* [[Floppy Cable]]

== Cartridges & Expansions ==
* [[Multicart by Prime (Phill Harvey-Smith)]]
* [[DragonMMC SDCard Interface by Prime (Phill Harvey-Smith)]]
* [[Dragon ROM/RAM Cartridge (Rink)]]
* [[Dragon I/O Cartridge (Rink)]]
* [[Dragon Multi Cartridge version 1.0 (Rolo)]]
* [[Dragon Multi Cartridge version 1.5 (Rolo)]]
* [[80 Column WordPak]] (CoCoDemus)
* [[Dragon Lab-Cartridge version 1.0 (Rolo)]]
* [[uDW SD-card DriveWire microserver]] (Tormod)

== 6809 DIY construction kits ==
Here a list of external DIY instructions to build a own 6809 based computer:

* [http://searle.hostei.com/grant/Multicomp/ Grant's Low-cost FPGA project "MULTICOMP"]
* [http://searle.hostei.com/grant/6809/Simple6809.html Grant's 6-chip 6809 computer]
* [http://www.msarnoff.org/projects/6809/ Ultim809: Homebrew 8-Bit Computer]
* [http://www.8bitforce.com/simon6809/ Simon 6809]
* [http://laurent68k.free.fr/Site/RedBoard6809.html HOMEBREW Computer 6809: RedBoard]

See also forums thread related to this list: http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=8&t=4338

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]]

UDW SD-card DriveWire microserver

2015-08-22T20:24:06Z

Tormod: new uDW page

File:Udw.jpg

2015-08-22T20:21:46Z

Tormod: uDW DriveWire microserver by Tormod

uDW DriveWire microserver by Tormod

DWLOAD

2015-08-22T17:05:24Z

Tormod: /* DriveWire overview */

== DriveWire overview ==

[[DriveWire]] is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like uDW can be used.

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive.

For Dragon there is also DWLOAD - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DWLOAD concept ==

DWLOAD is designed to be so small that it fits into unused parts of the Dragon BASIC ROM. Nonetheless, it allows you to simply download and run files from the DriveWire server from within BASIC without any resident use of memory. DWLOAD can be enhanced by "DriveWire Executable Extension Blocks" (dweebs) which are small program loaded from the server to provide further DriveWire capabilities on demand. Some examples are "VLOAD" to load files from VDK images residing on the DriveWire server, "LROM" to load a ROM image into high RAM, and "DOS" to boot NitrOS-9 over DriveWire.

DWLOAD can also be used together with HDB-DOS or Dragon DOS. You can for instance load files from the PC (plain files or from inside VDK images) and save them on your Dragon DOS floppy drive. Or load files from your Dragon DOS floppy drive and save them on the PC (currently only BASIC files supported via the "SAVE" dweeb).

== Requirements ==

In addition to your Dragon 32 or Dragon 64 or compatible home computer you will need either

DriveWire adapter + PC running DriveWire server (DW4)

or

uDW microserver

Of course, on the Dragon you will need DriveWire software. If you have the DWLOAD EPROM you are all set and can load everything (also HDB-DOS or NitrOS-9) via DriveWire. Otherwise, software (including a DWLOAD program) can be loaded from disk or cassette tape to get started.

== Using DWLOAD ==

DWLOAD is a small DriveWire client for BASIC which works without needing a DOS. It loads files as-is from the DriveWire server, that is, not using disk images like HDB-DOS or NitrOS-9 does.

Simply put: Just drop the files in your DriveWire4 server folder, and access them from the Dragon using DWLOAD.

The files can be Dragon DOS binary or BASIC files, or DECB binaries.

The DWLOAD client can be loaded from tape or disk or, most conveniently, embedded into the BASIC ROM, like the DWLOAD EPROM.

If you have the DWLOAD EPROM, use the "DLOAD" command to load files. Examples:

DLOAD"MYFILE.BAS"
to load and run the file "MYFILE.BAS" from the DriveWire server. To only load the program, use "DLOADN":
DLOADN"BROKEN.BAS"

Note that the filename ending is not significant, since the DWLOAD deduces the file type from its content.

== DWLOAD Extensible Execution Blocks (dweeb) ==

The DWLOAD client is relatively simple, due to the space constraints in the ROM. The dweeb is a mechanism to dynamically extend the functionality of DWLOAD. The dweeb is loaded from the server like any other program, but accesses the I/O routines of DWLOAD. It also reads its command parameters from the DWLOAD command line.

The best example is the "SAVE" dweeb. There is not enough room in the ROM to include support for saving files over DriveWire. However, this functionality can be loaded on demand. DLOAD"SAVE""MYFILE.BAS" saves a BASIC program to the DriveWire server. The SAVE functionality is only temporarily loaded into RAM and used during this invocation.

Another typical dweeb is "DOS" for booting an operating system (NitrOS-9), similar to the DOS command in HDB-DOS or the DWDOS program.

Pere has also created some dweebs for accessing VDK disk images on the DriveWire server, this is very useful for accessing Dragon DOS program collections without using a disk drive or DOS.

Since a dweeb uses the I/O routines of the calling DWLOAD, it is independent of the real transport being used, which makes development with for instance the Becker interface in XRoar very convenient.

Examples:

DLOAD"SAVE""MYFILE.BAS"

DLOAD"VLOAD""MYIMAGE.VDK""MYFILE.BAS"

DLOAD"DOS"

DLOAD"LROM""GAME.ROM"

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DWLOAD forum thread]

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968 dweebs forum thread]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Software]][[Category:Drivewire]]

DriveWire

2015-08-22T17:00:25Z

Tormod: /* DriveWire software */ link to DWLOAD and Drivewire for dummies

== Overview ==

DriveWire is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like uDW can be used.

== DriveWire software ==

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive. See [[Drivewire for dummies]] for how to use HDB-DOS and DriveWire.

For Dragon there is also [[DWLOAD]] - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DriveWire adapters ==

On the Dragon you will need an adapter to convert the printer port signals to a compatible serial port (or USB virtual serial port).

See [[Dragon_32/64_Drivewire_Adapter]].

== DriveWire servers ==

The Drivewire4 server is a Java application and can be downloaded here: https://sites.google.com/site/drivewire4/download

There exist also "DriveWire Lite": a reimplementation in C of the server side of the DriveWire 3 protocol: http://sourceforge.net/projects/dwlite/

There is also a OpenSource DriveWire Server written in Python: https://github.com/6809/DwLoadServer

== Drivewire4 (DW4) server usage ==

Just choose CoCo2 in the DriveWire4 server "Simple Config Wizard".
Keep all the default selections.

If you would like to use the server under Windows without installing the JRE, use this batch file for startup:
<pre>
SET JDK=%~dp0\jre
SET JAVA_EXE=%JDK%\bin\java.exe
"%JAVA_EXE%" -XX:+UseConcMarkSweepGC -jar DW4UI.jar --backup &
pause
</pre>
Download a JRE and put it into DriveWire directory together with this batch file.

[[Category:Documentation]] [[Category:Drivewire]]

Drivewire for dummies

2015-08-22T16:56:45Z

Tormod: this is HDB-DOS only, link to DriveWire page

Drivewire for Dummies - by Robert Hermanek
(originally posted on the CoCo mailing list)

NOTE: This is only about HDB-DOS - see [[DriveWire]] for more general information.

== Drivewire for Dummies - Part 1 ==

Background: Once upon a time, if you were lucky you had a color computer with a disk controller. (If not, you were biting your nails hoping your cassettes loaded.) If you had a disk system, then you could have up to 4 drives, and they were labelled drives 0 through 3, and you selected which disk drive you wanted to use with the drive command:

DRIVE n

Each of these four physical 5 1/4 floppies would store approximately 160k of data. Back in the day, this was pretty huge. Although disks were more reliable and much faster than cassette, disk failures or directory crashes were still quite common.

After the floppy era, hard drives started making an appearance. Harddrives are orders of magnitude larger (megs vs. kilobytes) however for usage in disk extended basic on a color computer, these larger devices would still have to be presented as "virtual floppies" of 160k each, so that a massive rewrite of DECB (disk extended color basic) would not be necessary, and also to avoid incompatibilities with old software.

HDB-DOS appeared on the scene eventually in order to facilitate connecting to a hard drive from DECB and getting access to your new space in friendly 160k virtual disks.

Next, some very clever folks (insert list of all the geniuses involved here) came up with "DriveWire." For the coco, it still comes down to be connected to some large "device." But in fact all read/write disk requests are redirected out the rs-232 port, and a server application on the far side (on a modern PC) will respond to the request and send data back to the coco. The coco sees this data as the response of a sector read (for example) from a floppy disk, just like back in the day when it was connected to actual coco disk drives via a disk controller.

For drivewire to work then, there are four things you need:
# a coco running HDB-DOS
# a cable connecting rs-232 to serial port on PC
# a drivewire server application running on the PC
# a disk image mounted and ready in the drivewire server app.

Now a little discussion of disk images, and people can correct me if I'm wrong.

Once, disk images (files with a DSK extension) were just a handy way of storing the data on a 35 track standard coco disk, so again about a 160k file. This file simply contains each track, each sector, in order, and the 256 bytes that make up each sector.

For the purpose of drivewire however, these DSK images started being placed in collections, since we didn't want to just work with one virtual floppy, but many virtual floppies.

Going back to the coco running HDB-DOS, there are now two commands for selecting which drive you want to access:

DRIVE n

This is the same command I mentioned above, and it will choose which virtual disk you want to use on the currently selected device. Now for original coco's running a disk controller, there was no talk of what device you wanted to access--you were accessing your disk controller, and if you were lucky you had more than one drive connected to it. You could then say DRIVE 0 or DRIVE 3 to access your disks.

When connecting to scsi devices came about, a new command was added:

DRIVE #n

Yes, looks the same except for the # symbol. This command selects which device you want to access. For example, if you had a scsi controller connected to your coco, with 2 physical harddrives attached, each of these harddrives would contain their own collections of virtual floppy disks. So all of the following are possible:

DRIVE #0
DRIVE 0 - first virtual disk on device 0
DRIVE 1 - next virutal disk on device 0
(etc)

DRIVE #1
DRIVE 0 - first virtual disk on device 1
DRIVE 1 - next virtual disk on device 1

(etc)

Now we get our sites back on drivewire, and here is what we come up with:

1) When you use the DRIVE #n command, you are selecting the "device," but for drivewire this simply means which source file (collection) of virtual floppies you wish to use. This collection is a single file (like a single physical harddrive back in the day) that contains, one after another, virtual floppy disk images.

2) When you use the DRIVE n command, you are choosing which virtual floppy on the currently selected collection you wish to use.

3) The real bonus: Back in the day with physical devices, you were limited to how many devices and disks you had by what you really had--in drivewire there is no limit other than the device and disk #'s have to be a byte value. That means you can select any device # 0 - 255 (DW4 server), and any drive # 0 to 255 on each device. 256 X 256 = 65,536 virtual disks that can be accessed by a coco connected to a drivewire server. That's a whole bunch of space!

So a final summary is:

# Get HDB-DOS running on coco, get server running on PC, get connected with a cable. (we'll get the specifics of the cable soon)
# In the server application, choose as many disk collections (that will be seen as "devices" in HDB-DOS) mounted as you would like.
# Select your current collection from the coco using the DRIVE #n command, and then choose your current virtual floppy disk using the DRIVE n command.

== Drivewire for Dummies - Part 2 - The Cable ==

Dragon Adapter
[[Dragon_32/64_Drivewire_Adapter]]

or

CoCo Drivewire Cable
http://www.mediafire.com/?c91gj67kw7q6yzu (CoCo DriveWire Serial Cable
pin-out diagrams)

== Drivewire for Dummies - Part 3 - Chicken and Egg ==

All the previous explanation assumes that you have HDB-DOS running on your coco. So how do you get it running on your coco?

1) If you have a disk system, you can get or create a physical disk that contains the HDB-DOS program. This includes a loader that basically gets HDB-DOS into RAM, then pulls the rug out from under DECB and replaces it with HDB-DOS. From then on you are accessing virtual disks through your rs-232 port instead of real disks through your controller cartridge.

There have been .DSK images posted here, that if restored to a physical floppy, would give you a nice HDB-DOS loader disk. However if you do not have drivewire already running, it can be pretty difficult to get the .DSK copied to a real floppy. There are PC utilities that can do this, assuming you have properly configured floppy drives on your PC (I've never gotten this to work myself.) Your best bet might be to have someone you know help you out and mail you a disk. Otherwise, does anyone know if you can still get a HDB-DOS disk from cloud9tech? That would be a valuable service I think...

2) You can load HDB-DOS loader from cassette. Now, you don't have to use an actual tape -- if you have a .WAV file on your PC that contains all the screeching and wailing we all know and love from our younger days, you can get the audio out on your PC connected to the audio in on your coco, then hit play on your .WAV file and "load" it into your coco. Or, you could play the .WAV onto an actual tape recorder if you wanted to load from a physical cassette. I feel like someone recently successfully loaded HDB-DOS using a .WAV file, if so, please reply directly to me with your audio file if you are willing--I'd like to test it myself, keep it on hand, and possibly help other drivewire newbies in the future...

3) You can burn an eprom with hdb-dos and place it in a cartridge so that it loads on boot. This is by far the most elegant, but also the most technically challenging. How to burn and install ROM images is a subject all its own, and I'm afraid I do not know enough about it. Again, cloud9tech will help you out, they did me!

== Drivewire for Dummies - Part 4 - DRIVE #n vs. DRIVE n ==

When it comes to daily usage, the most initially confusing thing about DriveWire I think is all this talk of "devices" versus "disks," and sometimes other terms are used. I'm not really sure what the best approach is to clarify this, but I'll take a shot at it...

First, it is unfortunate perhaps that we did not choose a different file extension for files that are collections of images, as opposed to a single image. If you have a .DSK file that contains a single image, this is what you will have (in terms of DECB):

35 tracks X 18 sectors X 256 bytes per sector = 161,280 bytes, or approximately a 160k file.

For the purposes of DriveWire, however, when you mount a .DSK file as DRIVE #0 for example (in the slot for device 0), this .DSK file is actually a collection of images, and as I mentioned before, perhaps we should have chosen a different file extension such as ".DEV" for "device" or "DWD" for drivewire disks (or something.) Regardless, this file is simple, and is just virtual disk images lined up one after another. The server application figures out what offset is necessary to find the right data.

An example: Let's say you mount file "MyUtils.DSK" in slot 0 on DriveWire server, and "MyGames.DSK" in slot 1 on DriveWire server. Then the following HDB-DOS commands on your CoCo will perform these functions:

DRIVE #0
-- selects MyUtils.DSK

DRIVE 0
-- will access first 160k disk, data starting at byte 1 through byte 161,280.

DRIVE 1
-- will access second disk, data starting at byte 161,281 through byte 322,560

DRIVE 2
-- will access third disk, data starting at byte 322,561 through byte 483,840

To access your games...

DRIVE #1
-- selects MyGames.DSK

Now, the DRIVE 0 command mentioned above will not give you access to the first disk on your Utils collection, but instead the first disk in your Games collection.

In the new Drivewire4 server application, it sounds like all these mappings can be changed as needed, but for this discussion I'm just assuming that DRIVE 0 through DRIVE 255 on the coco are mapped in the same order into a corresponding file on the server side.

This is basically all you need to know about DriveWire to access data from your PC... When I have a little more time, I'll try to list the commands for some of the more common things people do with Drivewire.

[[Category:Documentation]] [[Category:Hardware]] [[Category:Software]] [[Category:DIY_Projects]] [[Category:Drivewire]]

Dragon 32/64 Drivewire Adapter

2015-08-22T16:52:23Z

Tormod: link to DriveWire page

[[File:Drivewire.jpg]]‎

See also [[DriveWire]] and [[Drivewire_for_dummies]]

== Hardware ==

The built-in serial UART is the CP2102 from Silicon Labs.

== Windows ==

Windows driver can be downloaded from the chip manufacturer: http://www.silabs.com/products/mcu/pages/usbtouartbridgevcpdrivers.aspx

== Linux ==

In most cases, you simply need to run "sudo adduser $USER dialout". Read on for more details.

Some helpful commands:
<pre>
~ $ sudo lsusb | grep UART
Bus 001 Device 002: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light

$ dmesg | grep -ie cp210*
[17479.466698] usb 1-1: Product: CP2102 USB to UART Bridge Controller
[17479.548508] usbcore: registered new interface driver cp210x
[17479.548520] usbserial: USB Serial support registered for cp210x
[17479.548535] cp210x 1-1:1.0: cp210x converter detected
[17480.428168] usb 1-1: cp210x converter now attached to ttyUSB0
</pre>

Look at the last line, to see that the adapter is assigned to '''ttyUSB0'''. Check which groups have access to it:

<pre>
$ ls -l /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 0 Nov 11 13:15 /dev/ttyUSB0
</pre>
In this case you should assure that your user is in the user group '''dialout''', e.g.:
<pre>
$ groups # Display the user groups for the current user
user_foo : user_foo adm tty dialout fax cdrom floppy tape sudo audio dip video plugdev netdev fuse lpadmin scanner
</pre>
Is the group is not listed, add your user to the group, e.g:
<pre>
sudo adduser $USER dialout
</pre>

You will have to logout and relogin after this command!

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=781 DIY instructions]
* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DWLOAD]
* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=6&t=4270 buy a tormod's Drivewire Adapter]
* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=6&t=4854 buy a tormod's Drivewire deluxe cased adapters]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Drivewire]]

Technical

2015-08-22T16:51:22Z

Tormod: /* Informations */ add DriveWire link

'''PLEASE NOTE:'''
''The Dragon Archive and all of its contributors accept no liability for any injury or damage resulting from any persons attempting to use or follow any instructions contained within this section. The content is provided for information only and the resposibility for using that information lies with the individual performing the work.''

== Schematics ==

[[Dragon 32 Schematics]]

[[Dragon 64 Schematics]]

[[Project Alpha / Dragon Professional Schematics]]

[[Project Beta / Dragon 128 Schematics]]

[[Dragon DOS Schematic]]

[[Cumana DOS Schematic]]

== Hardware Pictures ==

[[Motherboard_Pictures|Motherboard Pictures]]

[[PSU_Pictures|PSU Pictures]]

[[Game_Cartridges|Cartridge PCB Pictures]].

== Service Sheets ==

[[Dragon 32 - Service Information (RWEW/KA/0080a)]]

[[Dragon 32 - Service Information (RWEW/KA/0081a)]]

[[Dragon 32 - Service Information (RWEW/RA/0082a) ]]

[[Dragon 32 - REPLACEMENT OF POWER SUPPLY AND CENTRAL PROCESSING UNITS ON THE DRAGON 32]]

[[Dragon 32 - CPU and PSU Modifcations and Compatibility]]

== N.D.U.G ==

[[Dragon 32 - 64K Upgrade]]

[[Dragon Notebook]]

== Tutorials ==

[[Importing images into the Dragon]]

== DIY Projects ==

[[Dragon Peripheral Controller (Electrónica Fácil magazine)]]<br>
[[Dragon 32 Input/Output Ports (Maplin Projects Book Eight)]]<br>
[[Dragon 32 RS232 Modem Interface (Maplin Projects Book Eight)]]

== Informations ==

* [[Keyboard]]
* [[CharMap]]
* [[Tokens]]
* [[DriveWire]]

Chips:

* [[MC6809E]] - Dragon CPU
* [[MC6847]] - Video Display Generator (VDG)
* [[SN74LS783]] - Synchronous Address Multiplexor (SAM)

Dragon 32/64 Drivewire Adapter

2015-08-22T16:48:52Z

Tormod: moved server software parts to new DriveWire page

[[File:Drivewire.jpg]]‎

See also: [[Drivewire_for_dummies]]

== Hardware ==

The built-in serial UART is the CP2102 from Silicon Labs.

== Windows ==

Windows driver can be downloaded from the chip manufacturer: http://www.silabs.com/products/mcu/pages/usbtouartbridgevcpdrivers.aspx

== Linux ==

In most cases, you simply need to run "sudo adduser $USER dialout". Read on for more details.

Some helpful commands:
<pre>
~ $ sudo lsusb | grep UART
Bus 001 Device 002: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x UART Bridge / myAVR mySmartUSB light

$ dmesg | grep -ie cp210*
[17479.466698] usb 1-1: Product: CP2102 USB to UART Bridge Controller
[17479.548508] usbcore: registered new interface driver cp210x
[17479.548520] usbserial: USB Serial support registered for cp210x
[17479.548535] cp210x 1-1:1.0: cp210x converter detected
[17480.428168] usb 1-1: cp210x converter now attached to ttyUSB0
</pre>

Look at the last line, to see that the adapter is assigned to '''ttyUSB0'''. Check which groups have access to it:

<pre>
$ ls -l /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 0 Nov 11 13:15 /dev/ttyUSB0
</pre>
In this case you should assure that your user is in the user group '''dialout''', e.g.:
<pre>
$ groups # Display the user groups for the current user
user_foo : user_foo adm tty dialout fax cdrom floppy tape sudo audio dip video plugdev netdev fuse lpadmin scanner
</pre>
Is the group is not listed, add your user to the group, e.g:
<pre>
sudo adduser $USER dialout
</pre>

You will have to logout and relogin after this command!

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=781 DIY instructions]
* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DWLOAD]
* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=6&t=4270 buy a tormod's Drivewire Adapter]
* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=6&t=4854 buy a tormod's Drivewire deluxe cased adapters]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Drivewire]]

DriveWire

2015-08-22T16:47:38Z

Tormod: new page

== Overview ==

DriveWire is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like uDW can be used.

== DriveWire software ==

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive.

For Dragon there is also DWLOAD - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DriveWire adapters ==

On the Dragon you will need an adapter to convert the printer port signals to a compatible serial port (or USB virtual serial port).

See [[Dragon_32/64_Drivewire_Adapter]].

== DriveWire servers ==

The Drivewire4 server is a Java application and can be downloaded here: https://sites.google.com/site/drivewire4/download

There exist also "DriveWire Lite": a reimplementation in C of the server side of the DriveWire 3 protocol: http://sourceforge.net/projects/dwlite/

There is also a OpenSource DriveWire Server written in Python: https://github.com/6809/DwLoadServer

== Drivewire4 (DW4) server usage ==

Just choose CoCo2 in the DriveWire4 server "Simple Config Wizard".
Keep all the default selections.

If you would like to use the server under Windows without installing the JRE, use this batch file for startup:
<pre>
SET JDK=%~dp0\jre
SET JAVA_EXE=%JDK%\bin\java.exe
"%JAVA_EXE%" -XX:+UseConcMarkSweepGC -jar DW4UI.jar --backup &
pause
</pre>
Download a JRE and put it into DriveWire directory together with this batch file.

[[Category:Documentation]] [[Category:Drivewire]]

DWLOAD

2015-08-22T16:34:37Z

Tormod: /* DWLOAD Extensible Execution Blocks (dweeb) */

== DriveWire overview ==

DriveWire is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like uDW can be used.
DriveWire software

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive.

For Dragon there is also DWLOAD - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DWLOAD concept ==

DWLOAD is designed to be so small that it fits into unused parts of the Dragon BASIC ROM. Nonetheless, it allows you to simply download and run files from the DriveWire server from within BASIC without any resident use of memory. DWLOAD can be enhanced by "DriveWire Executable Extension Blocks" (dweebs) which are small program loaded from the server to provide further DriveWire capabilities on demand. Some examples are "VLOAD" to load files from VDK images residing on the DriveWire server, "LROM" to load a ROM image into high RAM, and "DOS" to boot NitrOS-9 over DriveWire.

DWLOAD can also be used together with HDB-DOS or Dragon DOS. You can for instance load files from the PC (plain files or from inside VDK images) and save them on your Dragon DOS floppy drive. Or load files from your Dragon DOS floppy drive and save them on the PC (currently only BASIC files supported via the "SAVE" dweeb).

== Requirements ==

In addition to your Dragon 32 or Dragon 64 or compatible home computer you will need either

DriveWire adapter + PC running DriveWire server (DW4)

or

uDW microserver

Of course, on the Dragon you will need DriveWire software. If you have the DWLOAD EPROM you are all set and can load everything (also HDB-DOS or NitrOS-9) via DriveWire. Otherwise, software (including a DWLOAD program) can be loaded from disk or cassette tape to get started.

== Using DWLOAD ==

DWLOAD is a small DriveWire client for BASIC which works without needing a DOS. It loads files as-is from the DriveWire server, that is, not using disk images like HDB-DOS or NitrOS-9 does.

Simply put: Just drop the files in your DriveWire4 server folder, and access them from the Dragon using DWLOAD.

The files can be Dragon DOS binary or BASIC files, or DECB binaries.

The DWLOAD client can be loaded from tape or disk or, most conveniently, embedded into the BASIC ROM, like the DWLOAD EPROM.

If you have the DWLOAD EPROM, use the "DLOAD" command to load files. Examples:

DLOAD"MYFILE.BAS"
to load and run the file "MYFILE.BAS" from the DriveWire server. To only load the program, use "DLOADN":
DLOADN"BROKEN.BAS"

Note that the filename ending is not significant, since the DWLOAD deduces the file type from its content.

== DWLOAD Extensible Execution Blocks (dweeb) ==

The DWLOAD client is relatively simple, due to the space constraints in the ROM. The dweeb is a mechanism to dynamically extend the functionality of DWLOAD. The dweeb is loaded from the server like any other program, but accesses the I/O routines of DWLOAD. It also reads its command parameters from the DWLOAD command line.

The best example is the "SAVE" dweeb. There is not enough room in the ROM to include support for saving files over DriveWire. However, this functionality can be loaded on demand. DLOAD"SAVE""MYFILE.BAS" saves a BASIC program to the DriveWire server. The SAVE functionality is only temporarily loaded into RAM and used during this invocation.

Another typical dweeb is "DOS" for booting an operating system (NitrOS-9), similar to the DOS command in HDB-DOS or the DWDOS program.

Pere has also created some dweebs for accessing VDK disk images on the DriveWire server, this is very useful for accessing Dragon DOS program collections without using a disk drive or DOS.

Since a dweeb uses the I/O routines of the calling DWLOAD, it is independent of the real transport being used, which makes development with for instance the Becker interface in XRoar very convenient.

Examples:

DLOAD"SAVE""MYFILE.BAS"

DLOAD"VLOAD""MYIMAGE.VDK""MYFILE.BAS"

DLOAD"DOS"

DLOAD"LROM""GAME.ROM"

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DWLOAD forum thread]

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968 dweebs forum thread]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Software]][[Category:Drivewire]]

DWLOAD

2015-08-22T16:32:50Z

Tormod: /* Links */ Add link to forum thread on dweebs

== DriveWire overview ==

DriveWire is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like uDW can be used.
DriveWire software

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive.

For Dragon there is also DWLOAD - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DWLOAD concept ==

DWLOAD is designed to be so small that it fits into unused parts of the Dragon BASIC ROM. Nonetheless, it allows you to simply download and run files from the DriveWire server from within BASIC without any resident use of memory. DWLOAD can be enhanced by "DriveWire Executable Extension Blocks" (dweebs) which are small program loaded from the server to provide further DriveWire capabilities on demand. Some examples are "VLOAD" to load files from VDK images residing on the DriveWire server, "LROM" to load a ROM image into high RAM, and "DOS" to boot NitrOS-9 over DriveWire.

DWLOAD can also be used together with HDB-DOS or Dragon DOS. You can for instance load files from the PC (plain files or from inside VDK images) and save them on your Dragon DOS floppy drive. Or load files from your Dragon DOS floppy drive and save them on the PC (currently only BASIC files supported via the "SAVE" dweeb).

== Requirements ==

In addition to your Dragon 32 or Dragon 64 or compatible home computer you will need either

DriveWire adapter + PC running DriveWire server (DW4)

or

uDW microserver

Of course, on the Dragon you will need DriveWire software. If you have the DWLOAD EPROM you are all set and can load everything (also HDB-DOS or NitrOS-9) via DriveWire. Otherwise, software (including a DWLOAD program) can be loaded from disk or cassette tape to get started.

== Using DWLOAD ==

DWLOAD is a small DriveWire client for BASIC which works without needing a DOS. It loads files as-is from the DriveWire server, that is, not using disk images like HDB-DOS or NitrOS-9 does.

Simply put: Just drop the files in your DriveWire4 server folder, and access them from the Dragon using DWLOAD.

The files can be Dragon DOS binary or BASIC files, or DECB binaries.

The DWLOAD client can be loaded from tape or disk or, most conveniently, embedded into the BASIC ROM, like the DWLOAD EPROM.

If you have the DWLOAD EPROM, use the "DLOAD" command to load files. Examples:

DLOAD"MYFILE.BAS"
to load and run the file "MYFILE.BAS" from the DriveWire server. To only load the program, use "DLOADN":
DLOADN"BROKEN.BAS"

Note that the filename ending is not significant, since the DWLOAD deduces the file type from its content.

== DWLOAD Extensible Execution Blocks (dweeb) ==

The DWLOAD client is relatively simple, due to the space constraints in the ROM. The dweeb is a mechanism to dynamically extend the functionality of DWLOAD. The dweeb is loaded from the server like any other program, but accesses the I/O routines of DWLOAD. It also reads its command parameters from the DWLOAD command line.

The best example is the "SAVE" dweeb. There is not enough room in the ROM to include support for saving files over DriveWire. However, this functionality can be loaded on demand. DLOAD"SAVE""MYFILE.BAS" saves a BASIC program to the DriveWire server. The SAVE functionality is only temporarily loaded into RAM and used during this invocation.

Another typical dweeb is "DOS" for booting an operating system (NitrOS-9), similar to the DOS command in HDB-DOS or the DWDOS program.

Pere has also created some dweebs for accessing VDK disk images on the DriveWire server, this is very useful for accessing Dragon DOS program collections without using a disk drive or DOS.

Since a dweeb uses the I/O routines of the calling DWLOAD, it is independent of the real transport being used, which makes development with for instance the Becker interface in XRoar very convenient.

Examples:

DLOAD"SAVE""MYFILE.BAS"

DLOAD"VLOAD""MYIMAGE.VDK""MYFILE.BAS

DLOAD"DOS"

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DWLOAD forum thread]

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4968 dweebs forum thread]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Software]][[Category:Drivewire]]

DWLOAD

2015-08-22T16:31:05Z

Tormod: Add my own DWLOAD information

== DriveWire overview ==

DriveWire is a way to connect your Dragon to a PC. It allows you to transfer files from the PC to your Dragon, or to use the PC as a virtual disk for the Dragon. A server program runs on the PC and services requests from the Dragon. Instead of a PC, a stand-alone DriveWire server like uDW can be used.
DriveWire software

DriveWire on the Dragon uses the printer port. On the Dragon, software is needed that can "talk" to the DriveWire server through the printer port. Operating systems like HDB-DOS and NitrOS-9 have support for DriveWire, and can use the DriveWire server as a full replacement for a normal floppy or hard disk drive.

For Dragon there is also DWLOAD - a small program that can be used to load programs from the DriveWire server without needing a disk operating system. DWLOAD can be embedded in a modified BASIC ROM, replacing the "DLOAD" command.

== DWLOAD concept ==

DWLOAD is designed to be so small that it fits into unused parts of the Dragon BASIC ROM. Nonetheless, it allows you to simply download and run files from the DriveWire server from within BASIC without any resident use of memory. DWLOAD can be enhanced by "DriveWire Executable Extension Blocks" (dweebs) which are small program loaded from the server to provide further DriveWire capabilities on demand. Some examples are "VLOAD" to load files from VDK images residing on the DriveWire server, "LROM" to load a ROM image into high RAM, and "DOS" to boot NitrOS-9 over DriveWire.

DWLOAD can also be used together with HDB-DOS or Dragon DOS. You can for instance load files from the PC (plain files or from inside VDK images) and save them on your Dragon DOS floppy drive. Or load files from your Dragon DOS floppy drive and save them on the PC (currently only BASIC files supported via the "SAVE" dweeb).

== Requirements ==

In addition to your Dragon 32 or Dragon 64 or compatible home computer you will need either

DriveWire adapter + PC running DriveWire server (DW4)

or

uDW microserver

Of course, on the Dragon you will need DriveWire software. If you have the DWLOAD EPROM you are all set and can load everything (also HDB-DOS or NitrOS-9) via DriveWire. Otherwise, software (including a DWLOAD program) can be loaded from disk or cassette tape to get started.

== Using DWLOAD ==

DWLOAD is a small DriveWire client for BASIC which works without needing a DOS. It loads files as-is from the DriveWire server, that is, not using disk images like HDB-DOS or NitrOS-9 does.

Simply put: Just drop the files in your DriveWire4 server folder, and access them from the Dragon using DWLOAD.

The files can be Dragon DOS binary or BASIC files, or DECB binaries.

The DWLOAD client can be loaded from tape or disk or, most conveniently, embedded into the BASIC ROM, like the DWLOAD EPROM.

If you have the DWLOAD EPROM, use the "DLOAD" command to load files. Examples:

DLOAD"MYFILE.BAS"
to load and run the file "MYFILE.BAS" from the DriveWire server. To only load the program, use "DLOADN":
DLOADN"BROKEN.BAS"

Note that the filename ending is not significant, since the DWLOAD deduces the file type from its content.

== DWLOAD Extensible Execution Blocks (dweeb) ==

The DWLOAD client is relatively simple, due to the space constraints in the ROM. The dweeb is a mechanism to dynamically extend the functionality of DWLOAD. The dweeb is loaded from the server like any other program, but accesses the I/O routines of DWLOAD. It also reads its command parameters from the DWLOAD command line.

The best example is the "SAVE" dweeb. There is not enough room in the ROM to include support for saving files over DriveWire. However, this functionality can be loaded on demand. DLOAD"SAVE""MYFILE.BAS" saves a BASIC program to the DriveWire server. The SAVE functionality is only temporarily loaded into RAM and used during this invocation.

Another typical dweeb is "DOS" for booting an operating system (NitrOS-9), similar to the DOS command in HDB-DOS or the DWDOS program.

Pere has also created some dweebs for accessing VDK disk images on the DriveWire server, this is very useful for accessing Dragon DOS program collections without using a disk drive or DOS.

Since a dweeb uses the I/O routines of the calling DWLOAD, it is independent of the real transport being used, which makes development with for instance the Becker interface in XRoar very convenient.

Examples:

DLOAD"SAVE""MYFILE.BAS"

DLOAD"VLOAD""MYIMAGE.VDK""MYFILE.BAS

DLOAD"DOS"

== Links ==

* [http://archive.worldofdragon.org/phpBB3/viewtopic.php?f=5&t=4964 DWLOAD Forum Thread]

[[Category:Documentation]] [[Category:Hardware]] [[Category:DIY_Projects]] [[Category:Software]][[Category:Drivewire]]

Category:Drivewire

2015-08-22T15:58:01Z

Tormod:

All pages about Drivewire

The Dragon Composer

2015-04-11T10:46:50Z

Tormod: add manual cover page

{| align="right" valign="top"
|{{Infobox Game
|Image = [[Image:DragonComposer_Screenshot01.png|center|300px]]
|Gamenumber =
|Company = [[Microdeal]]
|Developer =
|Publisher = [[Microdeal]]
|Musician =
|Release = [[:Category:Game_1983|1983]]
|Platform = [[Dragon 32]] or [[Dragon 64]]
|Genre = Music
|Gamemode = 1P
|Operation = {{Keyboard}}
|Media = {{Cassette}}
|Language = {{EN}}
|Info =
}}
|}

The Dragon Composer is a music program by [[Microdeal]]. It compiles a basic file with the melody into machine code and allows playing them back and modify parameters such as tempo.

== Screenshots ==

[[File:DragonComposer_Screenshot02.png|300px|Screen02]][[File:DragonComposer_Screenshot03.png|300px|Screen03]]

== Packaging ==

[[File:DragonComposer.jpg|500px|Cover]]<br>
[[File:DragonComposer_Tape.jpg|300px|Cassette]]
[[File:Composer-manual-cover-bw.jpg|300px|Manual cover page]]

== Downloads ==
* [http://archive.worldofdragon.org/archive/index.php?dir=Tapes/Dragon/cas/&file=The%20Dragon%20Composer%20%281983%29%28Microdeal%29%5B%21%5D.zip The Dragon Composer] (Zipped .CAS file)

[[Category:Games]] [[Category:Game_Online]] [[Category:Game_1983]] [[Category:Music]]

File:Composer-manual-cover-bw.jpg

2015-04-11T10:43:56Z

Tormod:

Dragonstikka

2015-04-11T10:34:24Z

Tormod: add cover of all my issues

== Dragonstikka ==

* Publisher: Dragonklubben (Nesbru, Norway)
* Editors: Ole Garm & Erik Hicks

[[Image:Dragonstikka-cover-1985nr3.jpg|200px]]
[[Image:Dragonstikka-cover-1985nr5.jpg|200px]]
[[Image:Dragonstikka-cover-1985nr6.jpg|200px]]
[[Image:Dragonstikka-cover-1985nr7.jpg|200px]]
[[Image:Dragonstikka-cover-1985nr8.jpg|200px]]
[[Image:Dragonstikka-cover-1985nr9.jpg|200px]]
[[Image:Dragonstikka-cover-1986nr1.jpg|200px]]
[[Image:Dragonstikka-cover-1986nr2.jpg|200px]]
[[Image:Dragonstikka-cover-1986nr3.jpg|200px]]
[[Image:Dragonstikka-cover-1986nr4.jpg|200px]]

===Issues===
1985:
* Nr.1 ?
* Nr.2 ?
* Nr.3
* Nr.4 ?
* Nr.5
* Nr.6
* Nr.7
* Nr.8
* Nr.9/10
1986:
* Nr.1
* Nr.2 (March)
* Nr.3 (May)
* Nr.4 (October)

Program Library (Programbiblioteket) 3/1985
* 1 A Roadrace
* 2 B Regnskap
* 3 B Tegning
* 4 B Kalkyler
* 5 A Squash
* 6 A Enarmet banditt
* 7 A Lunar Lander

Program Library (Programbiblioteket) 7/1985
* 1 A Roadrace O.Garm
* 2 B Regnskap O.Garm
* 3 B Tegning O.Garm
* 4 A Enarmet banditt E.Hicks
* 5 A Lunar Lander O.Garm
* 6 A Bygderennet S.Aurlund & R.Nomedal
* 7 A 3D-Maze T.Olsen
* 8 C/D Klokka O.Garm
* 9 A Island O.Garm
* 10 A Romkamp O.Garm
* 11 A Dragonflight J.Baustad
* 12 A Lander J.Baustad
* 13 A Sjokkmann J.Baustad
* 14 D Hires-2 R.Michelsen
* 15 A Hangman R.Michelsen
* 16 A Geografi O.Garm

File:Dragonstikka-cover-1986nr4.jpg

2015-04-11T10:22:00Z

Tormod: