; ; 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 "cbm_kernal.inc" .include "c64.inc" .macpack module ; ------------------------------------------------------------------------ ; Header. Includes jump table module_header _c64_swlink_ser ; Driver signature .byte $73, $65, $72 ; "ser" .byte SER_API_VERSION ; Serial API version number ; Library reference .addr $0000 ; Jump table .word SER_INSTALL .word SER_UNINSTALL .word SER_OPEN .word SER_CLOSE .word SER_GET .word SER_PUT .word SER_STATUS .word SER_IOCTL .word SER_IRQ ;---------------------------------------------------------------------------- ; 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 ;---------------------------------------------------------------------------- ; ; Global variables ; ; We reuse the RS232 zero page variables for the driver, since the ROM ; routines cannot be used together with this driver. RecvHead = $B5 ; Head of receive buffer RecvTail = $BD ; Tail of receive buffer RecvFreeCnt = $F7 ; Number of bytes in receive buffer SendHead = $F8 ; Head of send buffer SendTail = $F9 ; Tail of send buffer SendFreeCnt = $FA ; Number of bytes free in send buffer .bss Stopped: .res 1 ; Flow-stopped flag RtsOff: .res 1 ; ; 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 $02 ; 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 $09 ; SER_BAUD_3600 .byte $0A ; SER_BAUD_4800 .byte $0B ; 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 .code ;---------------------------------------------------------------------------- ; SER_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. SER_INSTALL: ; Deactivate DTR and disable 6551 interrupts lda #%00001010 sta ACIA_CMD ; Set up the nmi vector lda NMIVec ldy NMIVec+1 sta NmiSave+0 sty NmiSave+1 lda #NmiHandler SetNMI: sta NMIVec sty NMIVec+1 ; Done, return an error code lda #SER_ERR_OK .assert SER_ERR_OK = 0, error tax rts ;---------------------------------------------------------------------------- ; SER_UNINSTALL routine. Is called before the driver is removed from memory. ; Must return an SER_ERR_xx code in a/x. SER_UNINSTALL: ; Stop interrupts, drop DTR lda #%00001010 sta ACIA_CMD ; Restore NMI vector and return OK lda NmiSave+0 ldy NmiSave+1 jmp SetNMI ;---------------------------------------------------------------------------- ; PARAMS routine. A pointer to a ser_params structure is passed in ptr1. ; Must return an SER_ERR_xx code in a/x. SER_OPEN: ; Check if the handshake setting is valid ldy #SER_PARAMS::HANDSHAKE ; Handshake lda (ptr1),y cmp #SER_HS_HW ; This is all we support bne InvParam ; Initialize buffers jsr InitBuffers ; Set the value for the control register, which contains stop bits, word ; length and the baud rate. ldy #SER_PARAMS::BAUDRATE lda (ptr1),y ; Baudrate index tay lda BaudTable,y ; Get 6551 value bmi InvBaud ; Branch if rate not supported sta tmp1 ldy #SER_PARAMS::DATABITS ; Databits lda (ptr1),y tay lda BitTable,y ora tmp1 sta tmp1 ldy #SER_PARAMS::STOPBITS ; Stopbits lda (ptr1),y tay lda StopTable,y ora tmp1 ora #%00010000 ; Receiver clock source = baudrate sta ACIA_CTRL ; Set the value for the command register. We remember the base value in ; RtsOff, since we will have to manipulate ACIA_CMD often. ldy #SER_PARAMS::PARITY ; Parity lda (ptr1),y tay lda ParityTable,y ora #%00000001 ; DTR active sta RtsOff ora #%00001000 ; Enable receive interrupts sta ACIA_CMD ; Done lda #SER_ERR_OK .assert SER_ERR_OK = 0, error tax rts ; Invalid parameter InvParam: lda #SER_ERR_INIT_FAILED ldx #0 ; return value is char rts ; Baud rate not available InvBaud: lda #SER_ERR_BAUD_UNAVAIL ldx #0 ; return value is char rts ;---------------------------------------------------------------------------- ; SER_CLOSE: Close the port, disable interrupts and flush the buffer. Called ; without parameters. Must return an error code in a/x. ; SER_CLOSE: ; Stop interrupts, drop DTR lda #%00001010 sta ACIA_CMD ; Initalize buffers. Returns zero in a jsr InitBuffers ; Return OK lda #SER_ERR_OK .assert SER_ERR_OK = 0, error tax rts ;---------------------------------------------------------------------------- ; SER_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. ; SER_GET: ldx SendFreeCnt ; Send data if necessary inx ; X == $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 ; return value is char 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 ;---------------------------------------------------------------------------- ; SER_PUT: Output character in A. ; Must return an error code in a/x. ; SER_PUT: ; Try to send ldx SendFreeCnt inx ; X = $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 .assert SER_ERR_OK = 0, error tax rts ;---------------------------------------------------------------------------- ; SER_STATUS: Return the status in the variable pointed to by ptr1. ; Must return an error code in a/x. ; SER_STATUS: lda ACIA_STATUS ldx #0 sta (ptr1,x) .assert SER_ERR_OK = 0, error txa rts ;---------------------------------------------------------------------------- ; SER_IOCTL: Driver defined entry point. The wrapper will pass a pointer to ioctl ; specific data in ptr1, and the ioctl code in A. ; Must return an error code in a/x. ; SER_IOCTL: lda #SER_ERR_INV_IOCTL ; We don't support ioclts for now ldx #0 ; return value is char rts ;---------------------------------------------------------------------------- ; SER_IRQ: Not used on the C64 ; SER_IRQ = $0000 ;---------------------------------------------------------------------------- ; ; 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 #$08 ;(2) beq @L9 ;(2*) cld txa pha tya pha @L1: lda ACIA_DATA ;(4) data ;get byte and put into receive buffer ldy RecvTail ;(4) ldx RecvFreeCnt ;(4) beq @L3 ;(2*) Jump if no space in receive buffer sta RecvBuf,y ;(5) inc RecvTail ;(6) dec RecvFreeCnt ;(6) cpx #33 ;(2) check for buffer space low bcc @L2 ;(2*) jmp NMIEXIT ;(3) ; Assert flow control @L2: lda RtsOff ;(3) assert flow control if buffer space too low sta ACIA_CMD ;(4) command sta Stopped ;(3) @L3: jmp NMIEXIT ;(3) @L9: pla jmp NmiContinue ;---------------------------------------------------------------------------- ; Try to send a byte. Internal routine. A = TryHard .proc TryToSend sta tmp1 ; Remember tryHard flag @L0: lda SendFreeCnt cmp #$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 ;---------------------------------------------------------------------------- ; Initialize buffers InitBuffers: ldx #0 stx Stopped stx RecvHead stx RecvTail stx SendHead stx SendTail dex ; X = 255 stx RecvFreeCnt stx SendFreeCnt rts