68008 Assembly programming for the Sinclair QL 

The Sinclair QL (Quantum Leap) was supposed to be something special - intended as one of the first, and cheapest 68000 machines on the market - it could have brought 16 bit to budget users...

Unfortunately it was late, and the 'microdrives' it used for storage were buggy!

Rather strangely the QL uses a weird 8 bit version of the 68000 - it's command compatible with the regular 68000 - but it's cut down data bus makes it slower,  and has less memory capabilites... apparently Sinclair got the CPU cheap, but it didn't stop the QL from being a failure - that said, it's a curious combination of 8 bit and 16 bit, so is a bit of fun to play with!

The 68008 is a cut down 68000 - it's address bus and data bus are smaller (normal spec of 68k in brackets)

Cpu 68008 7.5mhz (cut down 68000)
Cpu Address Bus  20 bit (down from 24)
Cpu Data Bus 8 bit (down from 16)
Ram 128k - 1MB max (down from 16)
ROM 48k
Resolution 256x256 @ 8 color
512x256 @ 4 color
Sound chip ? 2 channel  - not emulated by QLAY

Sinclair QL Software Developer's Guide - Covers all the traps and the best detail of the hardware.
QL Manual (Introduction,Beginners,Concepts,Keywords) - basics of using the ql
Assembly Language on the Sinclair QL - decent beginners programming book

Memory Map
Note: the exact address of the sysem elements marked *  may vary depending on firmware and ram installed - these examples only based on a 128k system...
Also note: Screen 2 shares the same ram as the system - we can turn off the system with the commands:
    Trap #0
    ori #0700,sr
But this will render many of the other traps unusable

Address   Purpose Details
$00000 Onboard
48k Rom

$0C000 16K Rom

$10000 Onboard I/O
$18000 (R) RTC byte 0 / (W) RTC Reset
$18001 (R) RTC byte 1 / (W) RTC Step
$18002 (R) RTC byte 2 / (W) Transmit control
$18003 (R) RTC byte 3 / (W) IPC link control
$18020 (R) Microdrive/RS232c status / (W) Microdrive control
$18021 (R) Interrupt/IPC status / (W) Interrupt control
$18022 (R) Microdrive Track 1 / (W) Microdrive / RS232C data
$18023 (R) Microdrive Track 2 / (W) Display control
$18063 Screen Mode S---C-O- On Colordepth Screenpage
$20000 Screen 1 Screen Ram
$28000 Screen 2 /
system (systemvars*)
$2847C System stack pointer*
$28E00 Base of Common Heap*
$2BC00 Free area*
$30000 Running
Free area
$37200 Basic area*
$38000 User Stack pointer*
$38000 Prog data*
$40000 Add on ram
(up to 512k)

$C0000 Add on

$E0000 Add on Rom
(up to 128k)

End of address space

Traps 0-4 have special purposes for system events...

We can control the screen without traps, but keyboard and sound can only be done with them!

A summary of the traps is shown below, see Sinclair QL Software Developer's Guide for full details
Trap   Detail
0 Supervisor mode
1 QDOS manager
2 QDOS Simple I/O
3 QDOS Advanced I/O
4 QDOS basic
  Trap       D0            Name         Description
#1 $15 MT.ACLCK Adjust the clock
#1 $0A MT.ACTIV Activate a job
#1 $16 MT.ALBAS Allocate BASIC program area
#1 $18 MT.ALCHP Allocate common heap area
#1 $0C MT.ALLOC Allocate an area in a heap
#1 $0E MT.ALRES Allocate resident procedure area
#1 $12 MT.BAUD Set the baud rate
#1 $01 MT.CJOB Create a job in transient program area
#1 $10 MT.DMODE Set or read the display mode
#1 $06 MT.FREE Find largest contiguous free space that may be allocated in the transient program area
#1 $05 MT.FRJOB Force remove job from transient program area
#1 $00 MT.lNF System information
#1 $11 MT.lPCOM Send a command to the IPC (sound/keyboard)
#1 $02 MTJINF Information on a job
#1 $0D MT.LNKFR Link a free space (back) into a heap
#1 $1A MT.LXINT Link an external interrupt service routine
#1 $1C MT.LPOLL Link a polling 50/60 Hz service routine
#1 $1E MT.LSCHD Link a scheduler loop task
#1 $20 MT.LlOD Link an I/O device driver
#1 $22 MT.LDD Link or a directory device driver into the operating system
#1 $0B MT.PRIOR Change job priority
#1 $13 MT.RCLCK Read the clock
#1 $17 MT.REBAS Release BASIC program area
#1 $19 MT.RECHP Release common heap area
#1 $09 MT.RELJB Release a job
#1 $0F MT.RERES Release resident procedure area
#1 $04 MT.RJOB Remove job from transient program area
#1 $1B MT.RXINT Remove an external interrupt service routine a
#1 $1D MT.RPOLL Remove a polling 50/60 Hz service routine
#1 $1F MT.RSCHD Remove a scheduler loop task
#1 $21 MT.RIOD Remove an IO device driver
#1 $23 MT.RDD Remove a directory device driver from the operating system
#1 $14 MT.SCLCK Set the clock
#1 $08 MT.SUSJB Suspend a job
#1 $07 MT.TRAPV Set the per-job pointer to trap vectors
#2 $02 IO.CLOSE Close a channel
#2 $04 IO.DELET Delete a file
#2 $03 IO.FORMT Format a sectored medium
#2 $01 IO.OPEN Open a channel
#3 $40 FS.CHECK Check all pending operations on a file
#3 $41 FS.FLUSH Flush buffers for this file
#3 $47 FS.HEADR Read file header
#3 $46 FS.HEADS Set file header
#3 $48 FS.LOAD Load file into memory
#3 $45 FS.MDINF Get information about medium
#3 $42 FS.POSAB Position file pointer absolute
#3 $43 FS.POSRE Position file pointer relative
#3 $49 FS.SAVE Save file from memory
#3 $04 IO.EDLIN Edit a line of characters (console driver only)
#3 $01 IO.FBYTE Fetch a byte
#3 $02 IO.FLlNE fetch a line of characters terminated
#3 $03 IO.FSTRG fetch a string of bytes
#3 $00 IO.PEND Check for pending input
#3 $05 IO.SBYTE Send a byte
#3 $07 IO.SSTRG Send a string of bytes
#3 $0C SD.BORDR Set the border width and colour
#3 $20 SD.CLEAR clear all of window
#3 $21 SD.CLRBT clear top of window
#3 $22 SD.CLRLN clear bottom of window
#3 $23 SD.CLRRT clear cursor line
#3 $24 SD.CLRTP clear right hand end of cursor line
#3 $0E SD.CURE Enable the cursor
#3 $0F SO.CURS Suppress the cursor
#3 $09 SD.EXTOP Call an extended operation
#3 $2E SO.FILL Fill rectangular block in window
#3 $35 SD.FLOOD Turn area flood on and off
#3 $25 SD.FOUNT Set or reset the fount
#3 $1B SD.PAN pan all of window
#3 $1E SO.PANLN pan cursor line
#3 $1F SO.PANRT pan right hand end of cursor line
#3 $17 SD.PIXP Position cursor using pixel coordinates
#3 $30 SD.POINT Draw a point
#3 $31 SD.LINE Draw a line
#3 $32 SD.ARC Draw an arc
#3 $33 SD.ELlPS Draw an ellipse
#3 $34 SD.SCALE Set scale
#3 $36 SD.GCUR Set Graphics cursor pos
#3 $10 SD.POS absolute position
#3 $11 SD.NCOL tabulate
#3 $12 SD.NL newline
#3 $13 SD.NROW previous column
#3 $14 SD.PCOl next column
#3 $15 SD.PROW previous row
#3 $16 SD.TAB next row
#3 $0A SD.PXENQ enquiry in pixel coordinates
#3 $0B SD.CHENQ enquiry in character coordinates
#3 $26 SD.RECOL Recolour a window
#3 $18 SD.SCROL scroll all of window scroll
#3 $19 SO.SCRBT top of window scroll
#3 $1A SO.SCRTP bottom of window
#3 $2A SD.SETFL set flash
#3 $2B SD.SETUL set underscore
#3 $2C SD.SETMD Set the character writing or plotting mode
#3 $27 SO.SETPA set paper colour
#3 $28 SO.SETST set strip colour
#3 $29 SO.SETIN set ink colour
#3 $20 SD.SETST Set character size and spacing
#3 $0D SD.WDEF Redefine a window

System Vars
A pointer to the system vars can be returned using the commands shown to the right...
the pointer will be returned in A0
    move.l #$0,d0    ;Info (a0=Sysvars)
    Trap #1

Var   Pos     Length   Meaning
SV_IDENT $00 word identification word
SV_CHEAP $04 long base of common heap area
SV_CHPFR $08 long first free space in common heap area
SV_FREE $0C long base of free area
SV_BASIC $10 long base of basic area
SV_TRNSP $14 long base of transient program area
SV_TRNFR $18 long first free space in transient program area
SV_RESPR $1C long base of resident procedure area
SV_RAMT $20 long top of ram (+1)
SV_RAND $2E word random number
SV_POLLM $30 word count of poll interupts missed
SV_TVMOD $32 byte 0 if not TV display
SV_SCRST $33 byte screen status (0= active)
SV_MCSTA $34 byte current value of display control register
SV_PClNT $35 byte current value of interrupt control/mask register
SV_NETNR $37 byte network station number
SV_I2LST $38 long pointer to list of interrupt 2 drivers
SV_PLlST $3C long pointer to list of polled tasks
SV_SHLST $40 long pointer to list of scheduler tasks
SV_DRLST $44 long pointer to list of device drivers
SV_DDLST $48 long pointer to list of directory device drivers
SV_KEYQ $4C long pointer to a keyboard queue
SV_TRAPV $50 long pointer to the trap redirection table
SV_CAPS $88 word caps lock
SV_ARBUF $8A word autorepeat buffer
SV_ARDEL $8C word autorepeat delay
SV_ARFRQ $8E word autorepeat 1/freq
SV_ARCNT $90 word autorepeat count
SV_CQCH $92 word keyboard change queue character code
SV_SOUND $96 word sound status
SV_SER1C $98 long receive channel 1 queue address
SV_SER2C $9C long receive channel 2 queue address
SV_TMODE $AO byte ZX8302 transmit mode (includes baudrate)
SV_CSUB $A2 long subroutine to jump to on CAPSLOCK
SV_TIMO $A6 word timeout for switching transmit mode
SV_TIMOV $A8 word value of switching timeout (two characters)
SV_FSTAT $AA word flashing cursor status
SV_BTPNT $54 long pointer to most recent slave block entry
SV_BTBAS $58 long pointer to base of slave block table
SV_BTTOP $5C long pointer to top of slave block table
SV_JBTAG $60 word current value of job tag
SV_JBMAX $62 word highest current job number
SV_JBPNT $64 long pointer to current job table entry
SV_JBBAS $68 long pointer to base of job table
SV_JBTOP $6C long pointer to top of job table
SV_CHTAG $70 word current value of channel tag
SV_CHMAX $72 word highest current channel number
SV_CHPNT $74 long pointer to last channel checked
SV_CHBAS $78 long pointer to base of channel table
SV_CHTOP $7C long pointer to top of channel table
SV_MDRUN $EE byte which drive is running?
SV_MDCNT $EF byte microdrive run-up run-down counter
SV_MDDID $F0 8 bytes drive ID*4 of each microdrive
SV_MDSTA $F8 8 bytes status 0=no pending ops
SV_FSDEF $100 16*long pointers to file system physical definition
SV_FSLST $140 long pointer to list offile channel definitions

Screen Layout
The Screen is memory mapped from $20000-$28000,

There are two possible screen modes, configured by bit 3 of port $18063

setting a 0 give 4 colors at 512x256 with Black,Red,Green and White
setting a 1 give 8 colors at 256x256 with Black,  R, G B, C, M, Y and White

There is no palette - the colors are fixed.
4 Color mode:
F E D C B A 9 8 7 6 5 4 3 2 1 0
G7 G6 G5 G4 G3 G2 G1 G0 R7 R6 R5 R4 R3 R2 R1 R0

8 Color mode: (F is flashing)
F E D C B A 9 8 7 6 5 4 3 2 1 0
G3 F3 G2 F2 G1 F1 G0 F0 R3 B3 R2 B2 R1 B1 R0 B0

If we want to test for Vsync (the start of screen redraw) we need to use Port $18021... bit 3 will go high (1) when Vsync starts... we need to write a 1 to that same bit at the same port to clear the Vsync event...

Therefore, in effect we can write 255 to port $18021, then read from $18021 until it's nonzero to get the Vsync event.
    move.b #%11111111,$18021    ;Clear interrupt bits
    move.b $18021,d0            ;Read in interrupt state
    tst.b d0                    ;Wait for an interrupt
    beq waitVBlankAgain

 7   6   5   4   3   2   1   0 
 $18021 Read  B M R X F T  I  G  B=Baud state, M=Microdrive inactive, R=Rtc state, X=eXternal Interrupt, F=Frame vsync, T=Transmit interrupt, I=IPC Interface interrupt G=Gap interrupt (microdrive)
 $18021 Write  R F M X F T  I  G  R=tRansmit mask, F=interFace mask, M=gap Mask,X=reset eXternal Interrupt,F=reset Frame vsync, T=reset Transmit interrupt, I=reset IPC Interface interrupt G=reset Gap interrupt

Keyboard Layout
Reading in from the keboard has to be done with Trap 1 - command 9

We have to send a sequence of command bytes - with byte 6 as the row number - the trap will return a byte in D1 - with a bit high when the button is down.

An example of the command is shown to the right - this example will read in row 1
    lea keycommand,a3
    move.b #$11,d0
    Trap #1

    dc.b $09    ;0
    dc.b $01    ;1
    dc.l 0        ;2345
    dc.b 1        ;6    - Row
    dc.b 2        ;7

     1          2          4          8         16        32        64       128  
  7   Shift Ctrl Alt X V / N ,
6 8 2 6 Q E O T U
5 9 W I Tab R - Y
4 L 3 H 1 A P D J
3 I Caps K S F = G ;
2 | Z . C B pound M ~
1 Enter Left Up Esc Right \ Space Down
0 F4 F1 5 F2 F3 F5 4 7

Sound Commands
Sound commands have to be passed via the Bios, using the same kind of commands as with the keyboard.

You need to adjust the Pitch settings to change the sound, and you can change the randomness bits to make the sound distorted,

It seems it's not possible to change the volume!
        lea     SoundCommand,a3   ; These three lines
        move.b   #$11,d0    ; Stop the note
        trap    #1

        dc.b    $A                ; Command
        dc.b    8                ; Bytes to follow
        dc.l    $0000aaaa       ; Byte Parameters
        dc.b    0               ; Pitch 1
        dc.b    0               ; Pitch 2
        dc.w    0                ; interval between steps (0,0),
        dc.w     $FFFF             ; Duration (65535)
        dc.b    0                ; step in pitch (4bit) / wrap (4bit)
        dc.b    0                 ; randomness of step (4bit) / fuzziness (4bit)
        dc.b    1               ; No return parameters       
The sound chip has a special 'silent' command - it's similar to the sound command, but with fewer paramteres!         lea     SilentCommand,a3   ; These three lines
        move.b   #$11,d0    ; Stop the note
        trap    #1

        dc.b    $B                ; Command byte
        dc.b    0                ;Bytes to follow
        dc.l    $0              ; Send no data
        dc.b    1               
; No return parameters       

Learn Assembly for the Greatest Classic Processors:  Z80 - 6502 - 68000
Visit www.ChibiAkumas.com to get my games and their source code! | Support me on patreon