--- /dev/null
+;
+; Serial driver for the C64 using a Swiftlink or Turbo-232 cartridge.
+;
+; Ullrich von Bassewitz, 2003-04-18
+;
+; The driver is based on the cc65 rs232 module, which in turn is based on
+; Craig Bruce device driver for the Switftlink/Turbo-232.
+;
+; 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.
+;
+
+ .include "zeropage.inc"
+ .include "ser-kernel.inc"
+ .include "ser-error.inc"
+ .include "c64.inc"
+
+
+; ------------------------------------------------------------------------
+; Header. Includes jump table
+
+.segment "JUMPTABLE"
+
+; Driver signature
+
+ .byte $73, $65, $72 ; "ser"
+ .byte $00 ; Serial API version number
+
+; Jump table.
+
+ .word INSTALL
+ .word UNINSTALL
+ .word PARAMS
+ .word GET
+ .word PUT
+ .word PAUSE
+ .word UNPAUSE
+ .word STATUS
+ .word IOCTL
+
+;----------------------------------------------------------------------------
+; I/O definitions
+
+ACIA = $DE00
+ACIA_DATA = ACIA+0 ; Data register
+ACIA_STATUS = ACIA+1 ; Status register
+ACIA_CMD = ACIA+2 ; Command register
+ACIA_CTRL = ACIA+3 ; Control register
+ACIA_CLOCK = ACIA+7 ; Turbo232 external baud-rate generator
+
+;----------------------------------------------------------------------------
+;
+; Global variables
+;
+
+.bss
+DropCnt: .res 4 ; Number of bytes lost from rx buffer full
+Stopped: .res 1 ; Flow-stopped flag
+RtsOff: .res 1 ;
+Errors: .res 1 ; Number of bytes received in error, low byte
+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
+
+.rodata
+
+; Tables used to translate RS232 params into register values
+
+BaudTable: ; bit7 = 1 means setting is invalid
+ .byte $FF ; SER_BAUD_45_5
+ .byte $FF ; SER_BAUD_50
+ .byte $FF ; SER_BAUD_75
+ .byte $FF ; SER_BAUD_110
+ .byte $FF ; SER_BAUD_134_5
+ .byte $FF ; SER_BAUD_150
+ .byte $05 ; SER_BAUD_300
+ .byte $06 ; SER_BAUD_600
+ .byte $07 ; SER_BAUD_1200
+ .byte $FF ; SER_BAUD_1800
+ .byte $08 ; SER_BAUD_2400
+ .byte $FF ; SER_BAUD_3600
+ .byte $0A ; SER_BAUD_4800
+ .byte $FF ; SER_BAUD_7200
+ .byte $0C ; SER_BAUD_9600
+ .byte $0E ; SER_BAUD_19200
+ .byte $0F ; SER_BAUD_38400
+ .byte $FF ; SER_BAUD_57600
+ .byte $FF ; SER_BAUD_115200
+ .byte $FF ; SER_BAUD_230400
+
+BitTable:
+ .byte $60 ; SER_BITS_5
+ .byte $40 ; SER_BITS_6
+ .byte $20 ; SER_BITS_7
+ .byte $00 ; SER_BITS_8
+
+StopTable:
+ .byte $00 ; SER_STOP_1
+ .byte $80 ; SER_STOP_2
+
+ParityTable:
+ .byte $00 ; SER_PAR_NONE
+ .byte $20 ; SER_PAR_ODD
+ .byte $60 ; SER_PAR_EVEN
+ .byte $A0 ; SER_PAR_MARK
+ .byte $E0 ; SER_PAR_SPACE
+
+HandshakeTable: ; bit7 = 1 means that setting is invalid
+ .byte $FF ; SER_HS_NONE
+ .byte $00 ; SER_HS_HW
+ .byte $FF ; SER_HS_SW
+
+; Delay times: 32 byte-receive times in milliseconds, or 100 max.
+; Formula = 320,000 / baud. Invalid values do contain $FF.
+PauseTimes:
+ .byte $FF ; SER_BAUD_45_5
+ .byte $FF ; SER_BAUD_50
+ .byte $FF ; SER_BAUD_75
+ .byte $FF ; SER_BAUD_110
+ .byte $FF ; SER_BAUD_134_5
+ .byte $FF ; SER_BAUD_150
+ .byte 100 ; SER_BAUD_300
+ .byte 100 ; SER_BAUD_600
+ .byte 100 ; SER_BAUD_1200
+ .byte $FF ; SER_BAUD_1800
+ .byte 100 ; SER_BAUD_2400
+ .byte $FF ; SER_BAUD_3600
+ .byte 67 ; SER_BAUD_4800
+ .byte $FF ; SER_BAUD_7200
+ .byte 34 ; SER_BAUD_9600
+ .byte 17 ; SER_BAUD_19200
+ .byte 9 ; SER_BAUD_38400
+ .byte $FF ; SER_BAUD_57600
+ .byte $FF ; SER_BAUD_115200
+ .byte $FF ; SER_BAUD_230400
+
+
+.code
+
+;----------------------------------------------------------------------------
+; INSTALL routine. Is called after the driver is loaded into memory. If
+; possible, check if the hardware is present.
+; Must return an SER_ERR_xx code in a/x.
+
+INSTALL:
+
+; 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 NMIVec
+ ldy NMIVec+1
+ sta NmiSave+0
+ sty NmiSave+1
+ lda #<NmiHandler
+ ldy #>NmiHandler
+ sta NMIVec
+ sty NMIVec+1
+
+; Set default to 2400-8N1, enable interrupts
+
+ lda ACIA_DATA
+ lda ACIA_STATUS
+ lda #$18
+ sta ACIA_CTRL
+
+ lda #$01
+ sta RtsOff
+ ora #$08
+ sta ACIA_CMD
+ lda #$06
+ sta BaudCode
+
+; Done, return an error code
+
+ lda #SER_ERR_OK
+ tax
+ rts
+
+;----------------------------------------------------------------------------
+; UNINSTALL routine. Is called before the driver is removed from memory.
+; Must return an SER_ERR_xx code in a/x.
+
+UNINSTALL:
+
+; Stop interrupts, drop DTR
+
+ lda RtsOff
+ and #%11100010
+ ora #%00000010
+ sta ACIA_CMD
+
+; Restore NMI vector
+
+ lda NmiSave+0
+ ldy NmiSave+1
+ sta NMIVec
+ sty NMIVec+1
+
+; Flag uninitialized
+
+ lda #SER_ERR_OK
+ tax
+ rts
+
+;----------------------------------------------------------------------------
+; PARAMS routine. A pointer to a ser_params structure is passed in ptr1.
+; Must return an SER_ERR_xx code in a/x.
+
+PARAMS:
+ ldy #SER_PARAMS_BAUDRATE
+ lda (ptr1),y ; Baudrate index
+ tax
+ lda BaudTable,x ; Get 6551 value
+ bmi invalid ; Branch if rate not supported
+ sta tmp1
+
+ iny ; Databits
+ lda (ptr1),y
+ tax
+ lda BitTable,x
+ ora tmp1
+ sta tmp1
+
+ iny ; Stopbits
+ lda (ptr1),y
+ tax
+ lda StopTable,x
+ ora tmp1
+ sta tmp1
+
+ iny ; Parity
+ lda (ptr1),y
+ tax
+ lda ParityTable,x
+ ora tmp1
+ sta tmp1
+
+ iny ; Handshake
+ lda (ptr1),y
+ tax
+ lda HandshakeTable,x
+ bmi invalid
+
+
+
+
+
+
+;----------------------------------------------------------------------------
+;
+; 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:
+ and #%11100000 ; Save new parity
+ 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 #RS_ERR_BAUD_TOO_FAST
+ bne @L9
+
+; Set baud/parameters
+
+@L3: lda tmp1
+ and #$0f
+ tax
+ lda BaudTable,x
+ cmp #$ff
+ bne @L5
+ lda #RS_ERR_BAUD_NOT_AVAIL
+ bne @L9
+
+@L5: tax
+ and #$30
+ beq @L6
+ bit Turbo232
+ bmi @L6
+ lda #RS_ERR_BAUD_NOT_AVAIL
+ bne @L9
+
+@L6: lda tmp1
+ and #$0f
+ sta BaudCode
+ lda tmp1
+ and #%11100000
+ ora #%00010000
+ sta tmp1
+ txa
+ and #$0f
+ ora tmp1
+ sta ACIA_CTRL
+ txa
+ and #%00110000
+ beq @L7
+ lsr
+ lsr
+ lsr
+ lsr
+ eor #%00000011
+ sta ACIA_CLOCK
+
+; Set new parity
+
+@L7: lda tmp2
+ sta RtsOff
+ ora #%00001000
+ sta ACIA_CMD
+ lda #0
+@L9: ldx #0
+ rts
+
+.rodata
+
+BaudTable:
+ .byte $ff,$ff,$ff,$05,$06,$07,$08,$0a,$0c,$0e,$0f,$10,$20,$30,$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, $30=230.4
+.code
+
+;----------------------------------------------------------------------------
+; GET: Will fetch a character from the receive buffer and store it into the
+; variable pointer to by ptr1. If no data is available, SER_ERR_NO_DATA is
+; return.
+;
+
+GET:
+
+; Check for bytes to send
+
+ ldx SendFreeCnt
+ cpx #$ff
+ beq @L1
+ lda #$00
+ jsr TryToSend
+
+; Check for buffer empty
+
+@L1: lda RecvFreeCnt ; (25)
+ cmp #$ff
+ bne @L2
+ lda #SER_ERR_NO_DATA
+ ldx #0
+ rts
+
+; Check for flow stopped & enough free: release flow control
+
+@L2: ldx Stopped ; (34)
+ beq @L3
+ cmp #63
+ bcc @L3
+ lda #$00
+ sta Stopped
+ lda RtsOff
+ ora #%00001000
+ sta ACIA_CMD
+
+; Get byte from buffer
+
+@L3: ldx RecvHead ; (41)
+ lda RecvBuf,x
+ inc RecvHead
+ inc RecvFreeCnt
+ ldx #$00 ; (59)
+ sta (ptr1,x)
+ txa ; Return code = 0
+ rts
+
+;----------------------------------------------------------------------------
+; PUT: Output character in A.
+; Must return an error code in a/x.
+;
+
+PUT:
+
+; Try to send
+
+ ldx SendFreeCnt
+ cpx #$ff
+ beq @L2
+ pha
+ lda #$00
+ jsr TryToSend
+ pla
+
+; Put byte into send buffer & send
+
+@L2: ldx SendFreeCnt
+ bne @L3
+ lda #<SER_ERR_OVERFLOW ; X is already zero
+ rts
+
+@L3: ldx SendTail
+ sta SendBuf,x
+ inc SendTail
+ dec SendFreeCnt
+ lda #$ff
+ jsr TryToSend
+ lda #<SER_ERR_OK
+ tax
+ rts
+
+;----------------------------------------------------------------------------
+; PAUSE: Assert flow control and disable interrupts.
+; Must return an error code in a/x.
+;
+
+PAUSE:
+
+; Assert flow control
+
+ lda RtsOff
+ sta Stopped
+ sta ACIA_CMD
+
+; Delay for flow stop to be received
+
+ ldx BaudCode
+ ldy PauseTimes,x
+ jsr DelayMs
+
+; Stop rx interrupts
+
+ lda RtsOff
+ ora #$02
+ sta ACIA_CMD
+ lda #<SER_ERR_OK
+ tax
+ rts
+
+
+;----------------------------------------------------------------------------
+; UNPAUSE: Re-enable interrupts and release flow control.
+; Must return an error code in a/x.
+;
+
+UNPAUSE:
+
+; Re-enable rx interrupts & release flow control
+
+@L1: lda #$00
+ sta Stopped
+ lda RtsOff
+ ora #%00001000
+ sta ACIA_CMD
+
+; Poll for stalled char & exit
+
+ jsr PollReceive
+ lda #<SER_ERR_OK
+ tax
+ rts
+
+;----------------------------------------------------------------------------
+; STATUS: Return the status in the variable pointed to by ptr1.
+; Must return an error code in a/x.
+;
+
+STATUS:
+
+; Get status
+
+ lda ACIA_STATUS
+ ldy #0
+ sta (ptr1),y
+ jsr PollReceive ; bug-recovery hack
+ tya ; SER_ERR_OK
+ tax
+ 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:
+ pha
+ lda ACIA_STATUS ;(4) ;status ;check for byte received
+ and #$08 ;(2)
+ beq @L9 ;(2*)
+ cld
+ txa
+ pha
+ tya
+ pha
+ lda ACIA_STATUS ;(4) opt ;status ;check for receive errors
+ and #$07 ;(2) opt
+ beq @L1 ;(3*)opt
+ inc Errors ;(5^)opt
+@L1: lda ACIA_DATA ;(4) ;data ;get byte and put into receive buffer
+ ldy RecvTail ;(4)
+ ldx RecvFreeCnt ;(4)
+ beq @L3 ;(2*)
+ sta RecvBuf,y ;(5)
+ inc RecvTail ;(6)
+ dec RecvFreeCnt ;(6)
+ cpx #33 ;(2) ;check for buffer space low
+ bcc @L2 ;(2*)
+ jmp NMIEXIT ;(3)
+
+; Assert flow control
+
+@L2: lda RtsOff ;(3) ;assert flow control if buffer space too low
+ sta ACIA_CMD ;(4) ;command
+ sta Stopped ;(3)
+ jmp NMIEXIT ;(3)
+
+; Drop this char
+
+@L3: inc DropCnt+0 ; not time-critical
+ bne @L4
+ inc DropCnt+1
+ bne @L4
+ inc DropCnt+2
+ bne @L4
+ inc DropCnt+3
+@L4: jmp NMIEXIT
+
+@L9: pla
+ jmp NmiContinue
+
+;----------------------------------------------------------------------------
+; Try to send a byte. Internal routine. A = TryHard
+
+.proc TryToSend
+
+ sta tmp1 ; Remember tryHard flag
+@L0: lda SendFreeCnt
+ cmp #$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_STATUS
+ 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_DATA
+ inc SendHead
+ inc SendFreeCnt
+ jmp @L0
+
+.endproc
+
+;----------------------------------------------------------------------------
+;
+; 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.
+;
+
+.proc PollReceive
+
+ lda #$08
+ and ACIA_STATUS
+ beq @L9
+ and ACIA_STATUS
+ beq @L9
+ lda ACIA_DATA
+ ldx RecvFreeCnt
+ beq @L9
+ ldx RecvTail
+ sta RecvBuf,x
+ inc RecvTail
+ dec RecvFreeCnt
+@L9: rts
+
+.endproc
+
+;----------------------------------------------------------------------------
+;
+; 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:
+; delay for 1017 clock cycles
+;
+
+
+.proc DelayMs ;( .A=milliseconds )
+
+@L1: ldx #203 ;(2)
+@L2: dex ;(2)
+ bne @L2 ;(3) // 1017 cycles
+ dey
+ bne @L1
+ rts
+
+.endproc
+
+
+.end
+
+
+
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