.word INSTALL
.word UNINSTALL
- .word PARAMS
+ .word OPEN
+ .word CLOSE
.word GET
.word PUT
- .word PAUSE
- .word UNPAUSE
.word STATUS
.word IOCTL
; 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 ;
-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
.byte $A0 ; SER_PAR_MARK
.byte $E0 ; SER_PAR_SPACE
-; 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
;----------------------------------------------------------------------------
lda #%00001010
sta ACIA_CMD
-; Initialize buffers & control
-
-@L4: ldx #0
- stx RecvHead
- stx SendHead
- stx RecvTail
- stx SendTail
- stx Stopped
- dex ; X = 255
- stx RecvFreeCnt
- stx SendFreeCnt
-
-; Set up nmi's
+; Set up the nmi vector
lda NMIVec
ldy NMIVec+1
; PARAMS routine. A pointer to a ser_params structure is passed in ptr1.
; Must return an SER_ERR_xx code in a/x.
-PARAMS:
+OPEN:
-; First, check if the handshake setting is valid
+; 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.
lda BaudTable,y ; Get 6551 value
bmi InvBaud ; Branch if rate not supported
sta tmp1
- sty BaudCode ; Remember baud rate index
ldy #SER_PARAMS_DATABITS ; Databits
lda (ptr1),y
ldx #>SER_ERR_BAUD_UNAVAIL
rts
+;----------------------------------------------------------------------------
+; CLOSE: Close the port, disable interrupts and flush the buffer. Called
+; without parameters. Must return an error code in a/x.
+;
+
+CLOSE:
+
+; Stop interrupts, drop DTR
+
+ lda #%00001010
+ sta ACIA_CMD
+
+; Initalize buffers. Returns zero in a
+
+ jsr InitBuffers
+
+; Return OK
+
+ lda #<SER_ERR_OK
+ tax ; A is zero
+ rts
+
;----------------------------------------------------------------------------
; 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
+GET: ldx SendFreeCnt ; Send data if necessary
inx ; X == $FF?
beq @L1
lda #$00
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 #%00000010 ; Disable interrupts
- 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:
- lda ACIA_STATUS
- ldy #0
- sta (ptr1),y
- jsr PollReceive ; bug-recovery hack
- tya ; SER_ERR_OK
- tax
+STATUS: lda ACIA_STATUS
+ ldx #0
+ sta (ptr1,x)
+ txa ; SER_ERR_OK
rts
;----------------------------------------------------------------------------
; Must return an error code in a/x.
;
-IOCTL:
- lda #<SER_ERR_INV_IOCTL ; We don't support ioclts for now
+IOCTL: lda #<SER_ERR_INV_IOCTL ; We don't support ioclts for now
ldx #>SER_ERR_INV_IOCTL
rts
.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
-
+; Initialize buffers
+InitBuffers:
+ ldx #0
+ stx Stopped
+ stx RecvHead
+ stx RecvTail
+ stx SendHead
+ stx SendTail
+ dex ; X = 255
+ stx RecvFreeCnt
+ stx SendFreeCnt
+ rts
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