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robfinch |
; ============================================================================
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; __
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; \\__/ o\ (C) 2022 Robert Finch, Waterloo
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; \ __ / All rights reserved.
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; \/_// robfinch@opencores.org
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; ||
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;
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;
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; Serial port routines for a WDC6551 compatible circuit.
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;
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; This source file is free software: you can redistribute it and/or modify
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; it under the terms of the GNU Lesser General Public License as published
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; by the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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;
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; This source file is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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;
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see .
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;
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; ============================================================================
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;
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;------------------------------------------------------------------------------
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; Initialize serial port.
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;
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; Clear buffer indexes. Two bytes are used for the buffer index even though
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; only a single byte is needed. This is for convenience in calculating the
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; number of characters in the buffer, done later. The upper byte remains at
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; zero.
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; The port is initialized for 9600 baud, 1 stop bit and 8 bits data sent.
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; The internal baud rate generator is used.
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;
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; Parameters:
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; none
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; Modifies:
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; d
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; Returns:
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; none
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;------------------------------------------------------------------------------
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InitSerial:
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SerialInit:
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clra
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clrb
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std SerHeadRcv-1
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std SerTailRcv-1
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std SerHeadXmit-1
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std SerTailXmit-1
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clr SerRcvXon
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clr SerRcvXoff
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ldb #$09 ; dtr,rts active, rxint enabled, no parity
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stb ACIA+ACIA_CMD
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ldb #$1E ; baud 9600, 1 stop bit, 8 bit, internal baud gen
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stb ACIA+ACIA_CTRL
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ldb #$0A6 ; diable fifos, reset fifos
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stb ACIA+ACIA_CTRL2
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rts
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;------------------------------------------------------------------------------
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; SerialGetChar
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;
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; Check the serial port buffer to see if there's a char available. If there's
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; a char available then return it. If the buffer is almost empty then send an
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; XON.
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;
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; Stack Space:
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; 2 words
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; Parameters:
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; none
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; Modifies:
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; none
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; Returns:
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; d = character or -1
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;------------------------------------------------------------------------------
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SerialGetChar:
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pshs x
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sei ; disable interrupts
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bsr SerialRcvCount ; check number of chars in receive buffer
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cmpb #8 ; less than 8?
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bhi sgc2
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ldb SerRcvXon ; skip sending XON if already sent
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bne sgc2 ; XON already sent?
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ldb #XON ; if <8 send an XON
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clr SerRcvXoff ; clear XOFF status
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stb SerRcvXon ; flag so we don't send it multiple times
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stb ACIA+ACIA_TX
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sgc2:
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ldb SerHeadRcv ; check if anything is in buffer
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cmpb SerTailRcv
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beq sgcNoChars ; no?
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ldx #SerRcvBuf
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abx
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clra
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ldb ,x ; get byte from buffer
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inc SerHeadRcv ; 4k wrap around
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bra sgcXit
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sgcNoChars:
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ldd #-1
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sgcXit:
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cli
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puls x,pc
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;------------------------------------------------------------------------------
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; SerialPeekChar
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;
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; Check the serial port buffer to see if there's a char available. If there's
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; a char available then return it. But don't update the buffer indexes. No need
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; to send an XON here.
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;
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; Stack Space:
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; 0 words
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; Parameters:
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; none
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; Modifies:
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; none
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; Returns:
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; d = character or -1
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;------------------------------------------------------------------------------
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SerialPeekChar:
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pshs x
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sei
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ldb SerHeadRcv ; check if anything is in buffer
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cmpb SerTailRcv
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beq spcNoChars ; no?
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ldx #SerRcvBuf
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abx
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clra
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ldb ,x ; get byte from buffer
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bra spcXit
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spcNoChars:
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ldd #-1
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spcXit:
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cli
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puls x,pc
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;------------------------------------------------------------------------------
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; SerialPeekChar
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; Get a character directly from the I/O port. This bypasses the input
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; buffer.
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;
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; Stack Space:
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; 0 words
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; Parameters:
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; none
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; Modifies:
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; d
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; Returns:
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; d = character or -1
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;------------------------------------------------------------------------------
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SerialPeekCharDirect:
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; Disallow interrupts between status read and rx read.
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sei
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ldb ACIA+ACIA_STAT
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bitb #8 ; look for Rx not empty
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beq spcd0001
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clra
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ldb ACIA+ACIA_RX
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cli
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rts
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spcd0001:
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ldd #-1
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cli
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rts
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;------------------------------------------------------------------------------
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; SerialPutChar
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; Put a character to the serial transmitter. This routine blocks until the
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; transmitter is empty.
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;
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; Stack Space
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; 0 words
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; Parameters:
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; b = character to put
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; Modifies:
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; none
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;------------------------------------------------------------------------------
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SerialPutChar:
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pshs a
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spc0001:
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cli ; provide a window for an interrupt to occur
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sei
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; Between the status read and the transmit do not allow an
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; intervening interrupt.
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lda ACIA+ACIA_STAT ; wait until the uart indicates tx empty
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bita #16 ; bit #4 of the status reg
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beq spc0001 ; branch if transmitter is not empty
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stb ACIA+ACIA_TX ; send the byte
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cli
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puls a
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rts
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;------------------------------------------------------------------------------
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; Calculate number of character in input buffer
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;
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; Returns:
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; d = number of bytes in buffer.
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;------------------------------------------------------------------------------
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SerialRcvCount:
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clra
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ldb SerTailRcv
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subb SerHeadRcv
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bge srcXit
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ldd #$1000
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subd SerHeadRcv
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addd SerTailRcv
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srcXit:
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rts
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;------------------------------------------------------------------------------
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; Serial IRQ routine
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;
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; Keeps looping as long as it finds characters in the ACIA recieve buffer/fifo.
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; Received characters are buffered. If the buffer becomes full, new characters
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; will be lost.
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;
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; Parameters:
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; none
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; Modifies:
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; d,x
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; Returns:
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; none
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;------------------------------------------------------------------------------
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SerialIRQ:
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sirqNxtByte:
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ldb ACIA+ACIA_STAT ; check the status
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bitb #$08 ; bit 3 = rx full
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beq notRxInt
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ldb ACIA+ACIA_RX ; get data from Rx buffer to clear interrupt
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cmpb #CTRLT ; detect special keystroke
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bne sirq0001
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; bsr DumpTraceQueue
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sirq0001:
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lda SerTailRcv ; check if recieve buffer full
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inca
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cmpa SerHeadRcv
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beq sirqRxFull
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sta SerTailRcv ; update tail pointer
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deca ; backup
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exg a,b
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ldx #SerRcvBuf ; x = buffer address
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abx
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sta ,x ; store recieved byte in buffer
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tst SerRcvXoff ; check if xoff already sent
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bne sirqNxtByte
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bsr SerialRcvCount ; if more than 4080 chars in buffer
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cmpb #4080
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blo sirqNxtByte
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ldb #XOFF ; send an XOFF
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clr SerRcvXon ; clear XON status
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stb SerRcvXoff ; set XOFF status
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stb ACIA+ACIA_TX
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bra sirqNxtByte ; check the status for another byte
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sirqRxFull:
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notRxInt:
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rts
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nmeSerial:
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fcb "Serial",0
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;------------------------------------------------------------------------------
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; Put a string to the serial port.
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;
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; Parameters:
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; d = pointer to string
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; Modifies:
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; none
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; Returns:
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; none
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;------------------------------------------------------------------------------
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SerialPutString:
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pshs d,x
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tfr d,x
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sps2:
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ldb ,x
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beq spsXit
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inx
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bsr SerialPutChar
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bra sps2
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spsXit:
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puls d,x,pc
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;------------------------------------------------------------------------------
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; A little routine to test serial output.
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;
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; Parameters:
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; none
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; Modifies:
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; none
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; Returns:
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; none
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;------------------------------------------------------------------------------
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SerialOutputTest:
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pshs d
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ldd #msgSerialTest
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lbsr DisplayString
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bsr SerialInit
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sotst1:
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ldb #XON
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bsr SerialPutChar
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bsr SerialPutChar
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bsr SerialPutChar
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ldd #msgSerialTest
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bsr SerialPutString
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lbsr INCH
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cmpb #CTRLC
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bne sotst1
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puls d,pc
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msgSerialTest:
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fcb "Serial port test",CR,LF,0
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