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cc65/libsrc/cbm510/ser/cbm510-std.s
Colin Leroy-Mira 734541ee05 Serial: Optimize SER_GET
There is no need to TryToSend before getting the character. We
send bytes during SER_PUT, and if interrupted during sending, we
still try to do it at the beginning of the next SER_PUT.
2023-09-07 07:14:01 +02:00

443 lines
12 KiB
ArmAsm

;
; Serial driver for the builtin 6551 ACIA of the Commodore 510.
;
; Ullrich von Bassewitz, 2003-12-18
;
; 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 "../extzp.inc"
.include "ser-kernel.inc"
.include "ser-error.inc"
.include "cbm510.inc"
.macpack module
; ------------------------------------------------------------------------
; Header. Includes jump table
module_header _cbm510_std_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
;----------------------------------------------------------------------------
;
; Global variables
;
.bss
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 in send buffer
Stopped: .res 1 ; Flow-stopped flag
RtsOff: .res 1 ;
; Send and receive buffers: 256 bytes each
RecvBuf: .res 256
SendBuf: .res 256
.rodata
; Tables used to translate RS232 params into register values
BaudTable: ; bit7 = 1 means setting is invalid
.byte $FF ; SER_BAUD_45_5
.byte $01 ; SER_BAUD_50
.byte $02 ; SER_BAUD_75
.byte $03 ; SER_BAUD_110
.byte $04 ; SER_BAUD_134_5
.byte $05 ; SER_BAUD_150
.byte $06 ; SER_BAUD_300
.byte $07 ; SER_BAUD_600
.byte $08 ; SER_BAUD_1200
.byte $09 ; SER_BAUD_1800
.byte $0A ; SER_BAUD_2400
.byte $0B ; SER_BAUD_3600
.byte $0C ; SER_BAUD_4800
.byte $0D ; SER_BAUD_7200
.byte $0E ; SER_BAUD_9600
.byte $0F ; SER_BAUD_19200
.byte $FF ; 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.
;
; Since we don't have to manage the IRQ vector on the Plus/4, this is actually
; the same as:
;
; SER_UNINSTALL routine. Is called before the driver is removed from memory.
; Must return an SER_ERR_xx code in a/x.
; and:
;
; SER_CLOSE: Close the port, disable interrupts and flush the buffer. Called
; without parameters. Must return an error code in a/x.
;
SER_INSTALL:
SER_UNINSTALL:
SER_CLOSE:
; Deactivate DTR and disable 6551 interrupts
lda #%00001010
jsr write_cmd
; Done, return an error code
lda #SER_ERR_OK
.assert SER_ERR_OK = 0, error
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.
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
ldx #0
stx Stopped
stx RecvHead
stx RecvTail
stx SendHead
stx SendTail
dex ; X = 255
stx RecvFreeCnt
stx SendFreeCnt
; 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
ldy #ACIA::CTRL
jsr write
; 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
jsr write_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_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:
; Check for buffer empty
lda RecvFreeCnt
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
beq @L3
cmp #63
bcc @L3
lda #$00
sta Stopped
lda RtsOff
ora #%00001000
jsr write_cmd
; Get byte from buffer
@L3: ldx RecvHead
lda RecvBuf,x
inc RecvHead
inc RecvFreeCnt
ldx #$00
sta (ptr1,x)
txa ; Return code = 0
rts
;----------------------------------------------------------------------------
; SER_PUT: Output character in A.
; Must return an error code in a/x.
;
SER_PUT:
; Try to send
ldx SendFreeCnt
cpx #$FF ; Nothing to flush
beq @L2
pha
lda #$00
jsr TryToSend
pla
; Reload SendFreeCnt after TryToSend
ldx SendFreeCnt
bne @L2
lda #SER_ERR_OVERFLOW ; X is already zero
rts
; Put byte into send buffer & send
@L2: ldx SendTail
sta SendBuf,x
inc SendTail
dec SendFreeCnt
lda #$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 #$0F
sta IndReg
ldy #ACIA::STATUS
lda (acia),y
ldx #0
sta (ptr1,x)
lda IndReg
sta ExecReg
.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: Called from the builtin runtime IRQ handler as a subroutine. All
; registers are already save, no parameters are passed, but the carry flag
; is clear on entry. The routine must return with carry set if the interrupt
; was handled, otherwise with carry clear.
;
SER_IRQ:
lda #$0F
sta IndReg ; Switch to the system bank
ldy #ACIA::STATUS
lda (acia),y ; Check ACIA status for receive interrupt
and #$08
beq @L9 ; Jump if no ACIA interrupt (carry still clear)
ldy #ACIA::DATA
lda (acia),y ; Get byte from ACIA
ldx RecvFreeCnt ; Check if we have free space left
beq @L1 ; Jump if no space in receive buffer
ldy RecvTail ; Load buffer pointer
sta RecvBuf,y ; Store received byte in buffer
inc RecvTail ; Increment buffer pointer
dec RecvFreeCnt ; Decrement free space counter
cpx #33 ; Check for buffer space low
bcs @L9 ; Assert flow control if buffer space low
; Assert flow control if buffer space too low
@L1: lda RtsOff
ldy #ACIA::CMD
sta (acia),y
sta Stopped
sec ; Interrupt handled
; Done, switch back to the execution segment
@L9: lda ExecReg
sta IndReg
rts
;----------------------------------------------------------------------------
; Try to send a byte. Internal routine. A = TryHard
.proc TryToSend
sta tmp1 ; Remember tryHard flag
lda #$0F
sta IndReg ; Switch to the system bank
@L0: lda SendFreeCnt
cmp #$ff
beq @L2 ; Bail out
; Check for flow stopped
@L1: lda Stopped
bne @L2 ; Bail out
; Check that swiftlink is ready to send
ldy #ACIA::STATUS
lda (acia),y
and #$10
bne @L3
bit tmp1 ; Keep trying if must try hard
bmi @L1
; Switch back the bank and return
@L2: lda ExecReg
sta IndReg
rts
; Send byte and try again
@L3: ldx SendHead
lda SendBuf,x
ldy #ACIA::DATA
sta (acia),y
inc SendHead
inc SendFreeCnt
jmp @L0
.endproc
;----------------------------------------------------------------------------
; Write to the ACIA changing the indirect segment. Offset is in Y, value in A.
write_cmd:
ldy #ACIA::CMD
write: pha
lda #$0F
sta IndReg
pla
sta (acia),y
lda ExecReg
sta IndReg
rts