Dragon Notebook

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. 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 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.

       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 This produces through DREAM the following Data:

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 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.

       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

(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

FINDING ADDRESS OF M/CODE PROGRAM

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

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:

       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

ARROW KEYS

Checking that one of the four arrow keys has been used: 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) 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

   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

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.

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

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

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

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