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
33 NmiExit = $febc ;exit address for nmi
35 NmiExit = $ff33 ;exit address for nmi
42 ;----------------------------------------------------------------------------
48 DropCnt: .res 4 ; Number of bytes lost from rx buffer full
49 Initialized: .res 1 ; Flag indicating driver is initialized
50 Stopped: .res 1 ; Flow-stopped flag
52 Errors: .res 1 ; Number of bytes received in error, low byte
53 Turbo232: .res 1 ; Flag indicating turbo-232
54 HackedFlag: .res 1 ; Flag indicating hacked-crystal swiftlink
55 CpuSpeed: .res 1 ; In MHz
56 RecvHead: .res 1 ; Head of receive buffer
57 RecvTail: .res 1 ; Tail of receive buffer
58 RecvFreeCnt: .res 1 ; Number of bytes in receive buffer
59 SendHead: .res 1 ; Head of send buffer
60 SendTail: .res 1 ; Tail of send buffer
61 SendFreeCnt: .res 1 ; Number of bytes free in send buffer
62 BaudCode: .res 1 ; Current baud in effect
64 ; Send and receive buffers: 256 bytes each
69 NmiContinue: .byte $4c ; JMP instruction for NMI save -- continue
70 NmiSave: .res 2 ; normal NMI handler
72 ; Switftlink register offsets
73 RegData = 0 ; Data register
74 RegStatus = 1 ; Status register
75 RegCommand = 2 ; Command register
76 RegControl = 3 ; Control register
77 RegClock = 7 ; Turbo232 external baud-rate generator
79 ; Error codes. Beware: The codes must match the codes in the C header file
80 ErrNotInitialized = $01
89 ;----------------------------------------------------------------------------
91 ; unsigned char __fastcall__ rs232_init (char hacked);
92 ; /* Initialize the serial port, install the interrupt handler. The parameter
93 ; * must be true (non zero) for a hacked swiftlink and false (zero) otherwise.
98 bit Initialized ;** shut down if started
104 ;** set hacked-crystal
108 ;** check for turbo-232
118 ;** get C128/C64 cpu speed
130 ;** check for super-cpu at 20 MHz
139 ;** initialize buffers & control
163 ;** set default to 2400-8N1, enable interrupts
171 @L5: sta ACIA+RegControl
187 ;----------------------------------------------------------------------------
189 ; unsigned char __fastcall__ rs232_params (unsigned char params, unsigned char parity);
190 ; /* Set the port parameters. Use a combination of the #defined values above. */
192 ; Set communication parameters.
194 ; baud rates stops word | parity
195 ; --------------------- ----- ----- | ---------
196 ; $00=50 $08=9600 $00=1 $00=8 | $00=none
197 ; $01=110 $09=19200 $80=2 $20=7 | $20=odd
198 ; $02=134.5 $0a=38400 $40=6 | $60=even
199 ; $03=300 $0b=57600 $60=5 | $A0=mark
200 ; $04=600 $0c=115200 | $E0=space
201 ; $05=1200 $0d=230400
202 ; $06=2400 $0e=future
203 ; $07=4800 $0f=future
207 jsr CheckInitialized ;** check initialized
217 ; Check cpu speed against baud rate
231 @L2: lda #ErrBaudTooFast
234 ; Set baud/parameters
290 .byte $ff,$ff,$ff,$05,$06,$07,$08,$0a,$0c,$0e,$0f,$10,$20,$30,$ff,$ff
292 .byte $01,$03,$04,$06,$07,$08,$0a,$0c,$0e,$0f,$ff,$ff,$00,$ff,$ff,$ff
293 ;in: 0 1 2 3 4 5 6 7 8 9 a b c d e f
294 ;baud50 110 134 3 6 12 24 48 96 19 38 57 115 230 exp exp
295 ;out masks: $0F=Baud, val$FF=err
296 ; $30=t232ExtBaud: $00=none, $10=57.6, $20=115.2, $30=230.4
299 ;----------------------------------------------------------------------------
301 ; unsigned char __fastcall__ rs232_done (void);
302 ; /* Close the port, deinstall the interrupt hander. You MUST call this function
303 ; * before terminating the program, otherwise the machine may crash later. If
304 ; * in doubt, install an exit handler using atexit(). The function will do
305 ; * nothing, if it was already called.
311 bit Initialized ;** check initialized
314 ; Stop interrupts, drop DTR
335 ;----------------------------------------------------------------------------
337 ; unsigned char __fastcall__ rs232_get (char* B);
338 ; /* Get a character from the serial port. If no characters are available, the
339 ; * function will return RS_ERR_NO_DATA, so this is not a fatal error.
344 jsr CheckInitialized ; Check if initialized
348 ; Check for bytes to send
351 stx ptr1+1 ; Store pointer to received char
358 ; Check for buffer empty
367 ; Check for flow stopped & enough free: release flow control
379 ; Get byte from buffer
387 txa ; Return code = 0
390 ;----------------------------------------------------------------------------
392 ; unsigned char __fastcall__ rs232_put (char B);
393 ; /* Send a character via the serial port. There is a transmit buffer, but
394 ; * transmitting is not done via interrupt. The function returns
395 ; * RS_ERR_OVERFLOW if there is no space left in the transmit buffer.
400 jsr CheckInitialized ; Check initialized
414 ; Put byte into send buffer & send
432 ;----------------------------------------------------------------------------
434 ; unsigned char __fastcall__ rs232_pause (void);
435 ; /* Assert flow control and disable interrupts. */
444 ; Assert flow control
450 ; Delay for flow stop to be received
467 ; Delay times: 32 byte-receive times in milliseconds, or 100 max.
468 ; Formula = 320,000 / baud
470 .byte 100,100,100,100,100,100,100,067,034,017,009,006,003,002,001,001
471 ;in: 0 1 2 3 4 5 6 7 8 9 a b c d e f
472 ;baud50 110 134 3 6 12 24 48 96 19 38 57 115 230 exp exp
475 ;----------------------------------------------------------------------------
477 ; unsigned char __fastcall__ rs232_unpause (void);
478 ; /* Re-enable interrupts and release flow control */
487 ; Re-enable rx interrupts & release flow control
495 ; Poll for stalled char & exit
502 ;----------------------------------------------------------------------------
504 ; unsigned char __fastcall__ rs232_status (unsigned char* status,
505 ; unsigned char* errors);
506 ; /* Return the serial port status. */
523 jsr PollReceive ; bug-recovery hack
530 ;----------------------------------------------------------------------------
533 ; C128 NMI overhead=76 cycles: int=7, maxLatency=6, ROMenter=33, ROMexit=30
534 ; C64 NMI overhead=76 cycles: int=7, maxLatency=6, ROMenter=34, ROMexit=29
536 ; timing: normal=76+43+9=128 cycles, assertFlow=76+52+9=137 cycles
538 ; C128 @ 115.2k: 177 cycles avail (fast)
539 ; C64 @ 57.6k: 177 cycles avail, worstAvail=177-43? = 134
540 ; SCPU @ 230.4k: 868 cycles avail: for a joke!
546 lda ACIA+RegStatus ;(4) ;status ;check for byte received
555 lda ACIA+RegStatus ;(4) ;status ;check for byte received
559 lda ACIA+RegStatus ;(4) opt ;status ;check for receive errors
563 @L1: lda ACIA+RegData ;(4) ;data ;get byte and put into receive buffer
570 cpx #33 ;(2) ;check for buffer space low
574 ; Assert flow control
576 @L2: lda RtsOff ;(3) ;assert flow control if buffer space too low
577 sta ACIA+RegCommand ;(4) ;command
583 @L3: inc DropCnt+0 ;not time-critical
598 ;----------------------------------------------------------------------------
600 ; CheckInitialized - internal check if initialized
601 ; Set carry and an error code if not initialized, clear carry and do not
602 ; change any registers if initialized.
608 lda #ErrNotInitialized
616 ;----------------------------------------------------------------------------
617 ; Try to send a byte. Internal routine. A = TryHard
620 sta tmp1 ; Remember tryHard flag
625 ; Check for flow stopped
630 ;** check that swiftlink is ready to send
632 @L2: lda ACIA+RegStatus
635 bit tmp1 ;keep trying if must try hard
639 ;** send byte and try again
649 ;----------------------------------------------------------------------------
651 ; PollReceive - poll for rx char
652 ; This function is useful in odd cases where the 6551 has a character in
653 ; it but it fails to raise an NMI. It might be edge-triggering conditions?
654 ; Actually, I'm not entirely sure that this condition can still arrise, but
655 ; calling this function does no harm.
673 ;----------------------------------------------------------------------------
675 ; DelayMs : delay for given number of milliseconds
676 ; This implementation isn't very rigerous; it merely delays for the
677 ; approximate number of clock cycles for the processor speed.
679 ; repeat for number of milliseconds:
680 ; repeat for number of MHz of cpu speed:
681 ; delay for 1017 clock cycles
684 DelayMs: ;( .A=milliseconds )
688 bne @L3 ;(3) // 1017 cycles