rs232.s
;
; SwiftLink/Turbo-232 v0.90 device driver, by Craig Bruce, 14-Apr-1998.
;
; This software is Public Domain. It is in Buddy assembler format.
;
; This device driver uses the SwiftLink RS-232 Serial Cartridge, available from
; Creative Micro Designs, Inc, and also supports the extensions of the Turbo232
; Serial Cartridge. Both devices are based on the 6551 ACIA chip. It also
; supports the "hacked" SwiftLink with a 1.8432 MHz crystal.
;
; The code assumes that the kernal + I/O are in context. On the C128, call
; it from Bank 15. On the C64, don't flip out the Kernal unless a suitable
; NMI catcher is put into the RAM under then Kernal. For the SuperCPU, the
; interrupt handling assumes that the 65816 is in 6502-emulation mode.
;
;--------------------------------------------------------------------------
;
; Adapted for the use with the cc65 runtime library by
; Ullrich von Bassewitz (uz@musoftware.de) 02-May-1999.
;
; All external functions are C callable, the return value is an error code.
;
.importzp ptr1, ptr2, tmp1, tmp2
.import popa, popax
.export _rs232_init, _rs232_params, _rs232_done, _rs232_get
.export _rs232_put, _rs232_pause, _rs232_unpause, _rs232_status
useC64 = 1
.if useC64
NmiExit = $febc ;exit address for nmi
.else
NmiExit = $ff33 ;exit address for nmi
.endif
ACIA = $DE00
;----------------------------------------------------------------------------
;
; Global variables
;
.bss
DropCnt: .res 4 ; Number of bytes lost from rx buffer full
Initialized: .res 1 ; Flag indicating driver is initialized
Stopped: .res 1 ; Flow-stopped flag
RtsOff: .res 1 ;
Errors: .res 1 ; Number of bytes received in error, low byte
Turbo232: .res 1 ; Flag indicating turbo-232
HackedFlag: .res 1 ; Flag indicating hacked-crystal swiftlink
CpuSpeed: .res 1 ; In MHz
RecvHead: .res 1 ; Head of receive buffer
RecvTail: .res 1 ; Tail of receive buffer
RecvFreeCnt: .res 1 ; Number of bytes in receive buffer
SendHead: .res 1 ; Head of send buffer
SendTail: .res 1 ; Tail of send buffer
SendFreeCnt: .res 1 ; Number of bytes free in send buffer
BaudCode: .res 1 ; Current baud in effect
; Send and receive buffers: 256 bytes each
RecvBuf: .res 256
SendBuf: .res 256
.data
NmiContinue: .byte $4c ; JMP instruction for NMI save -- continue
NmiSave: .res 2 ; normal NMI handler
; Switftlink register offsets
RegData = 0 ; Data register
RegStatus = 1 ; Status register
RegCommand = 2 ; Command register
RegControl = 3 ; Control register
RegClock = 7 ; Turbo232 external baud-rate generator
; Error codes. Beware: The codes must match the codes in the C header file
ErrNotInitialized = $01
ErrBaudTooFast = $02
ErrBaudNotAvail = $03
ErrNoData = $04
ErrOverflow = $05
.code
;----------------------------------------------------------------------------
;
; unsigned char __fastcall__ rs232_init (char hacked);
; /* Initialize the serial port, install the interrupt handler. The parameter
; * must be true (non zero) for a hacked swiftlink and false (zero) otherwise.
; */
;
_rs232_init:
bit Initialized ;** shut down if started
bpl @L1
pha
jsr _rs232_done
pla
;** set hacked-crystal
@L1: sta HackedFlag
;** check for turbo-232
lda #$00
sta ACIA+RegControl
tax
lda ACIA+RegClock
beq @L3
dex
@L3: stx Turbo232
;** get C128/C64 cpu speed
.if useC64
lda #1
sta CpuSpeed
.else
lda $d030
and #$01
clc
adc #1
sta CpuSpeed
.endif
;** check for super-cpu at 20 MHz
bit $d0bc
bmi @L4
bit $d0b8
bvs @L4
lda #20
sta CpuSpeed
;** initialize buffers & control
@L4: lda #0
sta RecvHead
sta SendHead
sta RecvTail
sta SendTail
sta Errors
sta Stopped
lda #255
sta RecvFreeCnt
sta SendFreeCnt
;** set up nmi's
lda $318
ldy $319
sta NmiSave+0
sty NmiSave+1
lda #<NmiHandler
ldy #>NmiHandler
sta $318
sty $319
;** set default to 2400-8N1, enable interrupts
lda ACIA+RegData
lda ACIA+RegStatus
lda #$18
bit HackedFlag
bpl @L5
lda #$1a
@L5: sta ACIA+RegControl
lda #$01
sta RtsOff
ora #$08
sta ACIA+RegCommand
lda #$06
sta BaudCode
;** return
lda #$ff
sta Initialized
lda #$00
tax
rts
;----------------------------------------------------------------------------
;
; unsigned char __fastcall__ rs232_params (unsigned char params, unsigned char parity);
; /* Set the port parameters. Use a combination of the #defined values above. */
;
; Set communication parameters.
;
; baud rates stops word | parity
; --------------------- ----- ----- | ---------
; $00=50 $08=9600 $00=1 $00=8 | $00=none
; $01=110 $09=19200 $80=2 $20=7 | $20=odd
; $02=134.5 $0a=38400 $40=6 | $60=even
; $03=300 $0b=57600 $60=5 | $A0=mark
; $04=600 $0c=115200 | $E0=space
; $05=1200 $0d=230400
; $06=2400 $0e=future
; $07=4800 $0f=future
;
_rs232_params:
jsr CheckInitialized ;** check initialized
bcc @L1
rts
; Save new parity
@L1: and #%11100000
ora #%00000001
sta tmp2
; Check cpu speed against baud rate
jsr popa
sta tmp1
and #$0f
cmp #$0c
bcc @L3
ldx CpuSpeed
cpx #1+1
bcc @L2
cmp #$0c
beq @L3
cpx #4
bcs @L3
@L2: lda #ErrBaudTooFast
bne @L9
; Set baud/parameters
@L3: lda tmp1
and #$0f
tax
lda NormBauds,x
bit HackedFlag
bpl @L4
lda HackBauds,x
@L4: cmp #$ff
bne @L5
lda #ErrBaudNotAvail
bne @L9
@L5: tax
and #$30
beq @L6
bit Turbo232
bmi @L6
lda #ErrBaudNotAvail
bne @L9
@L6: lda tmp1
and #$0f
sta BaudCode
lda tmp1
and #%11100000
ora #%00010000
sta tmp1
txa
and #$0f
ora tmp1
sta ACIA+RegControl
txa
and #%00110000
beq @L7
lsr
lsr
lsr
lsr
eor #%00000011
sta ACIA+RegClock
; Set new parity
@L7: lda tmp2
sta RtsOff
ora #%00001000
sta ACIA+RegCommand
lda #0
@L9: ldx #0
rts
.rodata
NormBauds:
.byte $ff,$ff,$ff,$05,$06,$07,$08,$0a,$0c,$0e,$0f,$10,$20,$30,$ff,$ff
HackBauds:
.byte $01,$03,$04,$06,$07,$08,$0a,$0c,$0e,$0f,$ff,$ff,$00,$ff,$ff,$ff
;in: 0 1 2 3 4 5 6 7 8 9 a b c d e f
;baud50 110 134 3 6 12 24 48 96 19 38 57 115 230 exp exp
;out masks: $0F=Baud, val$FF=err
; $30=t232ExtBaud: $00=none, $10=57.6, $20=115.2, $30=230.4
.code
;----------------------------------------------------------------------------
;
; unsigned char __fastcall__ rs232_done (void);
; /* Close the port, deinstall the interrupt hander. You MUST call this function
; * before terminating the program, otherwise the machine may crash later. If
; * in doubt, install an exit handler using atexit(). The function will do
; * nothing, if it was already called.
; */
;
_rs232_done:
bit Initialized ;** check initialized
bpl @L9
; Stop interrupts, drop DTR
lda RtsOff
and #%11100010
ora #%00000010
sta ACIA+RegCommand
; Restore NMI vector
lda NmiSave+0
ldy NmiSave+1
sta $318
sty $319
; Flag uninitialized
@L9: lda #$00
sta Initialized
tax
rts
;----------------------------------------------------------------------------
;
; unsigned char __fastcall__ rs232_get (char* B);
; /* Get a character from the serial port. If no characters are available, the
; * function will return RS_ERR_NO_DATA, so this is not a fatal error.
; */
;
_rs232_get:
jsr CheckInitialized ; Check if initialized
bcc @L1
rts
; Check for bytes to send
@L1: sta ptr1
stx ptr1+1 ; Store pointer to received char
ldx SendFreeCnt
cpx #$ff
beq @L2
lda #$00
jsr TryToSend
; Check for buffer empty
@L2: lda RecvFreeCnt
cmp #$ff
bne @L3
lda #ErrNoData
ldx #0
rts
; Check for flow stopped & enough free: release flow control
@L3: ldx Stopped
beq @L4
cmp #63
bcc @L4
lda #$00
sta Stopped
lda RtsOff
ora #%00001000
sta ACIA+RegCommand
; Get byte from buffer
@L4: ldx RecvHead
lda RecvBuf,x
inc RecvHead
inc RecvFreeCnt
ldx #$00
sta (ptr1,x)
txa ; Return code = 0
rts
;----------------------------------------------------------------------------
;
; unsigned char __fastcall__ rs232_put (char B);
; /* Send a character via the serial port. There is a transmit buffer, but
; * transmitting is not done via interrupt. The function returns
; * RS_ERR_OVERFLOW if there is no space left in the transmit buffer.
; */
;
_rs232_put:
jsr CheckInitialized ; Check initialized
bcc @L1
rts
; Try to send
@L1: ldx SendFreeCnt
cpx #$ff
beq @L2
pha
lda #$00
jsr TryToSend
pla
; Put byte into send buffer & send
@L2: ldx SendFreeCnt
bne @L3
lda #ErrOverflow
ldx #$00
rts
@L3: ldx SendTail
sta SendBuf,x
inc SendTail
dec SendFreeCnt
lda #$ff
jsr TryToSend
lda #$00
tax
rts
;----------------------------------------------------------------------------
;
; unsigned char __fastcall__ rs232_pause (void);
; /* Assert flow control and disable interrupts. */
;
_rs232_pause:
; Check initialized
jsr CheckInitialized
bcc @L1
rts
; Assert flow control
@L1: lda RtsOff
sta Stopped
sta ACIA+RegCommand
; Delay for flow stop to be received
ldx BaudCode
lda PauseTimes,x
jsr DelayMs
; Stop rx interrupts
lda RtsOff
ora #$02
sta ACIA+RegCommand
lda #0
tax
rts
.rodata
; Delay times: 32 byte-receive times in milliseconds, or 100 max.
; Formula = 320,000 / baud
PauseTimes:
.byte 100,100,100,100,100,100,100,067,034,017,009,006,003,002,001,001
;in: 0 1 2 3 4 5 6 7 8 9 a b c d e f
;baud50 110 134 3 6 12 24 48 96 19 38 57 115 230 exp exp
.code
;----------------------------------------------------------------------------
;
; unsigned char __fastcall__ rs232_unpause (void);
; /* Re-enable interrupts and release flow control */
;
_rs232_unpause:
; Check initialized
jsr CheckInitialized
bcc @L1
rts
; Re-enable rx interrupts & release flow control
@L1: lda #$00
sta Stopped
lda RtsOff
ora #%00001000
sta ACIA+RegCommand
; Poll for stalled char & exit
jsr PollReceive
lda #0
tax
rts
;----------------------------------------------------------------------------
;
; unsigned char __fastcall__ rs232_status (unsigned char* status,
; unsigned char* errors);
; /* Return the serial port status. */
;
_rs232_status:
sta ptr2
stx ptr2+1
jsr popax
sta ptr1
stx ptr1+1
jsr CheckInitialized
bcs @L9
; Get status
lda ACIA+RegStatus
ldy #0
sta (ptr1),y
jsr PollReceive ; bug-recovery hack
lda Errors
sta (ptr2),y
tya
tax
@L9: rts
;----------------------------------------------------------------------------
;
; NMI handler
; C128 NMI overhead=76 cycles: int=7, maxLatency=6, ROMenter=33, ROMexit=30
; C64 NMI overhead=76 cycles: int=7, maxLatency=6, ROMenter=34, ROMexit=29
;
; timing: normal=76+43+9=128 cycles, assertFlow=76+52+9=137 cycles
;
; C128 @ 115.2k: 177 cycles avail (fast)
; C64 @ 57.6k: 177 cycles avail, worstAvail=177-43? = 134
; SCPU @ 230.4k: 868 cycles avail: for a joke!
;
NmiHandler:
.if useC64
pha
lda ACIA+RegStatus ;(4) ;status ;check for byte received
and #$08 ;(2)
beq @L9 ;(2*)
cld
txa
pha
tya
pha
.else
lda ACIA+RegStatus ;(4) ;status ;check for byte received
and #$08 ;(2)
beq NmiNorm ;(2*)
.endif
lda ACIA+RegStatus ;(4) opt ;status ;check for receive errors
and #$07 ;(2) opt
beq @L1 ;(3*)opt
inc Errors ;(5^)opt
@L1: lda ACIA+RegData ;(4) ;data ;get byte and put into receive buffer
ldy RecvTail ;(4)
ldx RecvFreeCnt ;(4)
beq @L3 ;(2*)
sta RecvBuf,y ;(5)
inc RecvTail ;(6)
dec RecvFreeCnt ;(6)
cpx #33 ;(2) ;check for buffer space low
bcc @L2 ;(2*)
jmp NmiExit ;(3)
; Assert flow control
@L2: lda RtsOff ;(3) ;assert flow control if buffer space too low
sta ACIA+RegCommand ;(4) ;command
sta Stopped ;(3)
jmp NmiExit ;(3)
; Drop this char
@L3: inc DropCnt+0 ;not time-critical
bne @L4
inc DropCnt+1
bne @L4
inc DropCnt+2
bne @L4
inc DropCnt+3
@L4: jmp NmiExit
@L9:
.if useC64
pla
.endif
jmp NmiContinue
;----------------------------------------------------------------------------
;
; CheckInitialized - internal check if initialized
; Set carry and an error code if not initialized, clear carry and do not
; change any registers if initialized.
;
CheckInitialized:
bit Initialized
bmi @L1
lda #ErrNotInitialized
ldx #0
sec
rts
@L1: clc
rts
;----------------------------------------------------------------------------
; Try to send a byte. Internal routine. A = TryHard
TryToSend:
sta tmp1 ; Remember tryHard flag
@L0: lda SendFreeCnt
cmp #$ff
beq @L3 ; Bail out
; Check for flow stopped
@L1: lda Stopped
bne @L3 ; Bail out
;** check that swiftlink is ready to send
@L2: lda ACIA+RegStatus
and #$10
bne @L4
bit tmp1 ;keep trying if must try hard
bmi @L0
@L3: rts
;** send byte and try again
@L4: ldx SendHead
lda SendBuf,x
sta ACIA+RegData
inc SendHead
inc SendFreeCnt
jmp @L0
;----------------------------------------------------------------------------
;
; PollReceive - poll for rx char
; This function is useful in odd cases where the 6551 has a character in
; it but it fails to raise an NMI. It might be edge-triggering conditions?
; Actually, I'm not entirely sure that this condition can still arrise, but
; calling this function does no harm.
;
PollReceive:
lda #$08
and ACIA+RegStatus
beq @L9
and ACIA+RegStatus
beq @L9
lda ACIA+RegData
ldx RecvFreeCnt
beq @L9
ldx RecvTail
sta RecvBuf,x
inc RecvTail
dec RecvFreeCnt
@L9: rts
;----------------------------------------------------------------------------
;
; DelayMs : delay for given number of milliseconds
; This implementation isn't very rigerous; it merely delays for the
; approximate number of clock cycles for the processor speed.
; Algorithm:
; repeat for number of milliseconds:
; repeat for number of MHz of cpu speed:
; delay for 1017 clock cycles
;
DelayMs: ;( .A=milliseconds )
@L1: ldy CpuSpeed
@L2: ldx #203 ;(2)
@L3: dex ;(2)
bne @L3 ;(3) // 1017 cycles
dey
bne @L2
sec
sbc #1
bne @L1
rts
.end
rs232.s.html; generated on Sat Oct 13 22:41:33 2001 by ca65html
uz@cc65.org