2 ; SwiftLink/Turbo-232 v0.90 device driver, by Craig Bruce, 14-Apr-1998.
4 ; This software is Public Domain. It is in Buddy assembler format.
6 ; This device driver uses the SwiftLink RS-232 Serial Cartridge, available from
7 ; Creative Micro Designs, Inc, and also supports the extensions of the Turbo232
8 ; Serial Cartridge. Both devices are based on the 6551 ACIA chip. It also
9 ; supports the "hacked" SwiftLink with a 1.8432 MHz crystal.
11 ; The code assumes that the kernal + I/O are in context. On the C128, call
12 ; it from Bank 15. On the C64, don't flip out the Kernal unless a suitable
13 ; NMI catcher is put into the RAM under then Kernal. For the SuperCPU, the
14 ; interrupt handling assumes that the 65816 is in 6502-emulation mode.
16 ;--------------------------------------------------------------------------
18 ; Adapted for the use with the cc65 runtime library by
19 ; Ullrich von Bassewitz (uz@musoftware.de) 02-May-1999.
21 ; All external functions are C callable, the return value is an error code.
25 .importzp ptr1, ptr2, tmp1, tmp2
27 .export _rs232_init, _rs232_params, _rs232_done, _rs232_get
28 .export _rs232_put, _rs232_pause, _rs232_unpause, _rs232_status
31 NmiExit = $ff33 ;exit address for nmi
37 ;----------------------------------------------------------------------------
43 DropCnt: .res 4 ; Number of bytes lost from rx buffer full
44 Initialized: .res 1 ; Flag indicating driver is initialized
45 Stopped: .res 1 ; Flow-stopped flag
47 Errors: .res 1 ; Number of bytes received in error, low byte
48 Turbo232: .res 1 ; Flag indicating turbo-232
49 HackedFlag: .res 1 ; Flag indicating hacked-crystal swiftlink
50 CpuSpeed: .res 1 ; In MHz
51 RecvHead: .res 1 ; Head of receive buffer
52 RecvTail: .res 1 ; Tail of receive buffer
53 RecvFreeCnt: .res 1 ; Number of bytes in receive buffer
54 SendHead: .res 1 ; Head of send buffer
55 SendTail: .res 1 ; Tail of send buffer
56 SendFreeCnt: .res 1 ; Number of bytes free in send buffer
57 BaudCode: .res 1 ; Current baud in effect
59 ; Send and receive buffers: 256 bytes each
64 NmiContinue: .byte $4c ; JMP instruction for NMI save -- continue
65 NmiSave: .res 2 ; normal NMI handler
67 ; Switftlink register offsets
68 RegData = 0 ; Data register
69 RegStatus = 1 ; Status register
70 RegCommand = 2 ; Command register
71 RegControl = 3 ; Control register
72 RegClock = 7 ; Turbo232 external baud-rate generator
74 ; Error codes. Beware: The codes must match the codes in the C header file
75 ErrNotInitialized = $01
84 ;----------------------------------------------------------------------------
86 ; unsigned char __fastcall__ rs232_init (char hacked);
87 ; /* Initialize the serial port, install the interrupt handler. The parameter
88 ; * must be true (non zero) for a hacked swiftlink and false (zero) otherwise.
93 bit Initialized ;** shut down if started
99 ;** set hacked-crystal
103 ;** check for turbo-232
113 ;** get C128 cpu speed
121 ;** check for super-cpu at 20 MHz
130 ;** initialize buffers & control
154 ;** set default to 2400-8N1, enable interrupts
162 @L5: sta ACIA+RegControl
178 ;----------------------------------------------------------------------------
180 ; unsigned char __fastcall__ rs232_params (unsigned char params, unsigned char parity);
181 ; /* Set the port parameters. Use a combination of the #defined values above. */
183 ; Set communication parameters.
185 ; baud rates stops word | parity
186 ; --------------------- ----- ----- | ---------
187 ; $00=50 $08=9600 $00=1 $00=8 | $00=none
188 ; $01=110 $09=19200 $80=2 $20=7 | $20=odd
189 ; $02=134.5 $0a=38400 $40=6 | $60=even
190 ; $03=300 $0b=57600 $60=5 | $A0=mark
191 ; $04=600 $0c=115200 | $E0=space
192 ; $05=1200 $0d=230400
193 ; $06=2400 $0e=future
194 ; $07=4800 $0f=future
198 jsr CheckInitialized ;** check initialized
208 ; Check cpu speed against baud rate
222 @L2: lda #ErrBaudTooFast
225 ; Set baud/parameters
281 .byte $ff,$ff,$ff,$05,$06,$07,$08,$0a,$0c,$0e,$0f,$10,$20,$30,$ff,$ff
283 .byte $01,$03,$04,$06,$07,$08,$0a,$0c,$0e,$0f,$ff,$ff,$00,$ff,$ff,$ff
284 ;in: 0 1 2 3 4 5 6 7 8 9 a b c d e f
285 ;baud50 110 134 3 6 12 24 48 96 19 38 57 115 230 exp exp
286 ;out masks: $0F=Baud, val$FF=err
287 ; $30=t232ExtBaud: $00=none, $10=57.6, $20=115.2, $30=230.4
290 ;----------------------------------------------------------------------------
292 ; unsigned char __fastcall__ rs232_done (void);
293 ; /* Close the port, deinstall the interrupt hander. You MUST call this function
294 ; * before terminating the program, otherwise the machine may crash later. If
295 ; * in doubt, install an exit handler using atexit(). The function will do
296 ; * nothing, if it was already called.
302 bit Initialized ;** check initialized
305 ; Stop interrupts, drop DTR
326 ;----------------------------------------------------------------------------
328 ; unsigned char __fastcall__ rs232_get (char* B);
329 ; /* Get a character from the serial port. If no characters are available, the
330 ; * function will return RS_ERR_NO_DATA, so this is not a fatal error.
335 jsr CheckInitialized ; Check if initialized
339 ; Check for bytes to send
342 stx ptr1+1 ; Store pointer to received char
349 ; Check for buffer empty
358 ; Check for flow stopped & enough free: release flow control
370 ; Get byte from buffer
378 txa ; Return code = 0
381 ;----------------------------------------------------------------------------
383 ; unsigned char __fastcall__ rs232_put (char B);
384 ; /* Send a character via the serial port. There is a transmit buffer, but
385 ; * transmitting is not done via interrupt. The function returns
386 ; * RS_ERR_OVERFLOW if there is no space left in the transmit buffer.
391 jsr CheckInitialized ; Check initialized
405 ; Put byte into send buffer & send
423 ;----------------------------------------------------------------------------
425 ; unsigned char __fastcall__ rs232_pause (void);
426 ; /* Assert flow control and disable interrupts. */
435 ; Assert flow control
441 ; Delay for flow stop to be received
458 ; Delay times: 32 byte-receive times in milliseconds, or 100 max.
459 ; Formula = 320,000 / baud
461 .byte 100,100,100,100,100,100,100,067,034,017,009,006,003,002,001,001
462 ;in: 0 1 2 3 4 5 6 7 8 9 a b c d e f
463 ;baud50 110 134 3 6 12 24 48 96 19 38 57 115 230 exp exp
466 ;----------------------------------------------------------------------------
468 ; unsigned char __fastcall__ rs232_unpause (void);
469 ; /* Re-enable interrupts and release flow control */
478 ; Re-enable rx interrupts & release flow control
486 ; Poll for stalled char & exit
493 ;----------------------------------------------------------------------------
495 ; unsigned char __fastcall__ rs232_status (unsigned char* status,
496 ; unsigned char* errors);
497 ; /* Return the serial port status. */
514 jsr PollReceive ; bug-recovery hack
521 ;----------------------------------------------------------------------------
524 ; C128 NMI overhead=76 cycles: int=7, maxLatency=6, ROMenter=33, ROMexit=30
525 ; C64 NMI overhead=76 cycles: int=7, maxLatency=6, ROMenter=34, ROMexit=29
527 ; timing: normal=76+43+9=128 cycles, assertFlow=76+52+9=137 cycles
529 ; C128 @ 115.2k: 177 cycles avail (fast)
530 ; C64 @ 57.6k: 177 cycles avail, worstAvail=177-43? = 134
531 ; SCPU @ 230.4k: 868 cycles avail: for a joke!
535 lda ACIA+RegStatus ;(4) ;status ;check for byte received
538 lda ACIA+RegStatus ;(4) opt ;status ;check for receive errors
542 @L1: lda ACIA+RegData ;(4) ;data ;get byte and put into receive buffer
549 cpx #33 ;(2) ;check for buffer space low
553 ; Assert flow control
555 @L2: lda RtsOff ;(3) ;assert flow control if buffer space too low
556 sta ACIA+RegCommand ;(4) ;command
562 @L3: inc DropCnt+0 ;not time-critical
573 ;----------------------------------------------------------------------------
575 ; CheckInitialized - internal check if initialized
576 ; Set carry and an error code if not initialized, clear carry and do not
577 ; change any registers if initialized.
583 lda #ErrNotInitialized
591 ;----------------------------------------------------------------------------
592 ; Try to send a byte. Internal routine. A = TryHard
595 sta tmp1 ; Remember tryHard flag
600 ; Check for flow stopped
605 ;** check that swiftlink is ready to send
607 @L2: lda ACIA+RegStatus
610 bit tmp1 ;keep trying if must try hard
614 ;** send byte and try again
623 ;----------------------------------------------------------------------------
625 ; PollReceive - poll for rx char
626 ; This function is useful in odd cases where the 6551 has a character in
627 ; it but it fails to raise an NMI. It might be edge-triggering conditions?
628 ; Actually, I'm not entirely sure that this condition can still arrise, but
629 ; calling this function does no harm.
647 ;----------------------------------------------------------------------------
649 ; DelayMs : delay for given number of milliseconds
650 ; This implementation isn't very rigerous; it merely delays for the
651 ; approximate number of clock cycles for the processor speed.
653 ; repeat for number of milliseconds:
654 ; repeat for number of MHz of cpu speed:
655 ; delay for 1017 clock cycles
658 DelayMs: ;( .A=milliseconds )
662 bne @L3 ;(3) // 1017 cycles