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632 lines
14 KiB
ArmAsm
632 lines
14 KiB
ArmAsm
;
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; SwiftLink/Turbo-232 v0.90 device driver, by Craig Bruce, 14-Apr-1998.
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;
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; This software is Public Domain. It is in Buddy assembler format.
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;
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; This device driver uses the SwiftLink RS-232 Serial Cartridge, available from
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; Creative Micro Designs, Inc, and also supports the extensions of the Turbo232
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; Serial Cartridge. Both devices are based on the 6551 ACIA chip. It also
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; supports the "hacked" SwiftLink with a 1.8432 MHz crystal.
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;
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; The code assumes that the kernal + I/O are in context. On the C128, call
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; it from Bank 15. On the C64, don't flip out the Kernal unless a suitable
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; NMI catcher is put into the RAM under then Kernal. For the SuperCPU, the
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; interrupt handling assumes that the 65816 is in 6502-emulation mode.
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;
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;--------------------------------------------------------------------------
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;
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; Adapted for the use with the cc65 runtime library by
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; Ullrich von Bassewitz (uz@musoftware.de) 02-May-1999.
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;
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; All external functions are C callable, the return value is an error code.
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;
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.importzp ptr1, ptr2, tmp1, tmp2
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.importzp acia, RecvBuf, SendBuf
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.import popa, popax
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.import sys_bank, restore_bank
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.export _rs232_init, _rs232_params, _rs232_done, _rs232_get
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.export _rs232_put, _rs232_pause, _rs232_unpause, _rs232_status
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.export k_rs232
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.include "zeropage.inc"
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;----------------------------------------------------------------------------
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;
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; Global variables
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;
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.bss
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DropCnt: .res 4 ; Number of bytes lost from rx buffer full
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Initialized: .res 1 ; Flag indicating driver is initialized
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Stopped: .res 1 ; Flow-stopped flag
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RtsOff: .res 1 ;
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Errors: .res 1 ; Number of bytes received in error, low byte
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BaudCode: .res 1 ; Current baud in effect
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; Segment, the RS232 buffers are in
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BufferSeg = 2
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; UART register offsets
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RegData = 0 ; Data register
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RegStatus = 1 ; Status register
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RegCommand = 2 ; Command register
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RegControl = 3 ; Control register
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; Error codes. Beware: The codes must match the codes in the C header file
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ErrNotInitialized = $01
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ErrBaudTooFast = $02
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ErrBaudNotAvail = $03
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ErrNoData = $04
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ErrOverflow = $05
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.code
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;----------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ rs232_init (char hacked);
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; /* Initialize the serial port, install the interrupt handler. The parameter
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; * must be true (non zero) for a hacked swiftlink and false (zero) otherwise.
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; */
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;
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_rs232_init:
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bit Initialized ;** shut down if started
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bpl @L1
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pha
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jsr _rs232_done
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pla
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; Initialize buffers & control
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@L1: lda #0
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sta RecvHead
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sta SendHead
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sta RecvTail
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sta SendTail
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sta Errors
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sta Stopped
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lda #255
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sta RecvFreeCnt
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sta SendFreeCnt
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; Set default to 2400-8N1, enable interrupts
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jsr sys_bank ; Switch indirect to system bank
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ldy #RegData
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lda (acia),y
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ldy #RegStatus
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lda (acia),y
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lda #$18
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ldy #RegControl
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sta (acia),y
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lda #$01
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sta RtsOff
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ora #$08
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ldy #RegCommand
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sta (acia),y
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lda #$06
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sta BaudCode
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jsr restore_bank
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lda #$ff
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sta Initialized
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lda #$00
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tax
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rts
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;----------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ rs232_params (unsigned char params, unsigned char parity);
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; /* Set the port parameters. Use a combination of the #defined values above. */
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;
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; Set communication parameters.
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;
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; baud rates stops word | parity
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; --------------------- ----- ----- | ---------
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; $00=50 $08=9600 $00=1 $00=8 | $00=none
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; $01=110 $09=19200 $80=2 $20=7 | $20=odd
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; $02=134.5 $0a=38400 $40=6 | $60=even
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; $03=300 $0b=57600 $60=5 | $A0=mark
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; $04=600 $0c=115200 | $E0=space
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; $05=1200 $0d=230400
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; $06=2400 $0e=future
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; $07=4800 $0f=future
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;
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_rs232_params:
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jsr CheckInitialized ;** check initialized
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bcc @L1
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rts
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; Save new parity
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@L1: and #%11100000
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ora #%00000001
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sta tmp2
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; Set baud/parameters
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jsr popa
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sta tmp1
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and #$0f
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tax
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lda Bauds,x
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cmp #$ff
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bne @L5
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lda #ErrBaudNotAvail
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bne @L9
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@L5: jsr sys_bank ; Indirect segment to system bank
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tax
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lda tmp1
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and #$0f
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sta BaudCode
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lda tmp1
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and #%11100000
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ora #%00010000
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sta tmp1
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txa
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and #$0f
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ora tmp1
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ldy #RegControl
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sta (acia),y
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; Set new parity
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@L7: lda tmp2
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sta RtsOff
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ora #%00001000
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ldy #RegCommand
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sta (acia),y
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jsr restore_bank ; Restore indirect bank
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lda #0
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@L9: ldx #0
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rts
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.rodata
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Bauds:
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.byte $01,$03,$04,$06,$07,$08,$0a,$0c,$0e,$0f,$ff,$ff,$ff,$ff,$ff,$ff
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;in: 0 1 2 3 4 5 6 7 8 9 a b c d e f
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;baud50 110 134 3 6 12 24 48 96 19 38 57 115 230 exp exp
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;out masks: $0F=Baud, val$FF=err
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.code
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;----------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ rs232_done (void);
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; /* Close the port, deinstall the interrupt hander. You MUST call this function
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; * before terminating the program, otherwise the machine may crash later. If
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; * in doubt, install an exit handler using atexit(). The function will do
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; * nothing, if it was already called.
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; */
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;
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_rs232_done:
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bit Initialized ;** check initialized
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bpl @L9
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; Stop interrupts, drop DTR
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lda RtsOff
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and #%11100010
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ora #%00000010
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ldx IndReg
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ldy #$0F
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sty IndReg ; Set indirect to system bank
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ldy #RegCommand
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sta (acia),y
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stx IndReg ; Restore old indirect bank
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; Flag uninitialized
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@L9: lda #$00
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sta Initialized
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tax
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rts
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;----------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ rs232_get (char* B);
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; /* Get a character from the serial port. If no characters are available, the
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; * function will return RS_ERR_NO_DATA, so this is not a fatal error.
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; */
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;
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_rs232_get:
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jsr CheckInitialized ; Check if initialized
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bcc @L1
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rts
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; Check for bytes to send
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@L1: sta ptr1
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stx ptr1+1 ; Store pointer to received char
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ldx SendFreeCnt
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cpx #$ff
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beq @L2
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lda #$00
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jsr TryToSend
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; Check for buffer empty
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@L2: lda RecvFreeCnt
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cmp #$ff
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bne @L3
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lda #ErrNoData
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ldx #0
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rts
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; Check for flow stopped & enough free: release flow control
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@L3: ldx Stopped
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beq @L4
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cmp #63
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bcc @L4
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lda #$00
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sta Stopped
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lda RtsOff
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ora #%00001000
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ldx IndReg
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ldy #$0F ; Set indirect to system bank
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sty IndReg
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ldy #RegCommand
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sta (acia),y
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stx IndReg
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; Get byte from buffer
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@L4: ldx IndReg
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lda #BufferSeg ; Set indirect to buffer bank
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sta IndReg
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ldy RecvHead
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lda (RecvBuf),y
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stx IndReg ; Restore indirect bank
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inc RecvHead
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inc RecvFreeCnt
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ldx #$00
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sta (ptr1,x)
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txa ; Return code = 0
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rts
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;----------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ rs232_put (char B);
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; /* Send a character via the serial port. There is a transmit buffer, but
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; * transmitting is not done via interrupt. The function returns
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; * RS_ERR_OVERFLOW if there is no space left in the transmit buffer.
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; */
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;
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_rs232_put:
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jsr CheckInitialized ; Check initialized
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bcc @L1
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rts
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; Try to send
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@L1: ldx SendFreeCnt
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cpx #$ff
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beq @L2
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pha
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lda #$00
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jsr TryToSend
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pla
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; Put byte into send buffer & send
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@L2: ldx SendFreeCnt
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bne @L3
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lda #ErrOverflow
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ldx #$00
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rts
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; There is enough room (character still in A)
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@L3: ldx IndReg
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ldy #BufferSeg ; Set indirect to buffer segment
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sty IndReg
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ldy SendTail
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sta (SendBuf),y
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stx IndReg ; Restore indirect bank
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inc SendTail
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dec SendFreeCnt
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lda #$ff
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jsr TryToSend
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lda #$00
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tax
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rts
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;----------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ rs232_pause (void);
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; /* Assert flow control and disable interrupts. */
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;
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_rs232_pause:
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; Check initialized
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jsr CheckInitialized
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bcc @L1
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rts
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; Assert flow control
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@L1: lda RtsOff
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sta Stopped
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jsr sys_bank ; Set indirect to system bank
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ldy #RegCommand
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sta (acia),y
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; Delay for flow stop to be received
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ldx BaudCode
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lda PauseTimes,x
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jsr DelayMs
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; Stop rx interrupts
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lda RtsOff
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ora #$02
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ldy #RegCommand
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sta (acia),y
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jsr restore_bank ; Restore indirect segment
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lda #0
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tax
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rts
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.rodata
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; Delay times: 32 byte-receive times in milliseconds, or 100 max.
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; Formula = 320,000 / baud
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PauseTimes:
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.byte 100,100,100,100,100,100,100,067,034,017,009,006,003,002,001,001
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;in: 0 1 2 3 4 5 6 7 8 9 a b c d e f
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;baud50 110 134 3 6 12 24 48 96 19 38 57 115 230 exp exp
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.code
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;----------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ rs232_unpause (void);
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; /* Re-enable interrupts and release flow control */
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;
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_rs232_unpause:
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; Check initialized
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jsr CheckInitialized
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bcc @L1
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rts
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; Re-enable rx interrupts & release flow control
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@L1: lda #$00
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sta Stopped
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lda RtsOff
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ora #%00001000
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ldx IndReg
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ldy #$0F
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sty IndReg ; Set indirect to system bank
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ldy #RegCommand
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sta (acia),y
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stx IndReg ; Restore indirect bank
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; Poll for stalled char & exit
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jsr PollReceive
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lda #0
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tax
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rts
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;----------------------------------------------------------------------------
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;
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; unsigned char __fastcall__ rs232_status (unsigned char* status,
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; unsigned char* errors);
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; /* Return the serial port status. */
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;
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_rs232_status:
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sta ptr2
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stx ptr2+1
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jsr popax
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sta ptr1
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stx ptr1+1
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jsr CheckInitialized
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bcs @L9
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; Get status
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ldx IndReg ; Save indirect segment
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lda #$0F
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sta IndReg ; Set system bank as indirect segment
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ldy #RegStatus
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lda (acia),y ; Read status register
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stx IndReg
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ldy #0
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sta (ptr1),y
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jsr PollReceive ; bug-recovery hack
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lda Errors
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ldy #0
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sta (ptr2),y
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tya
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tax
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@L9: rts
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;----------------------------------------------------------------------------
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;
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; RS232 interrupt handler.
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; The RS232 handler will be called with the system bank as indirect bank
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; and all registers saved.
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;
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k_rs232:
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ldy #RegStatus
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lda (acia),y ; check for byte received
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and #$08
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beq @L9 ; Nothing to receive
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lda (acia),y ; check for receive errors
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and #$07
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beq @L1
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inc Errors
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@L1: ldy #RegData
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lda (acia),y ; get byte and put into receive buffer
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ldx RecvFreeCnt
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beq @L3
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ldy #BufferSeg
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sty IndReg
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ldy RecvTail
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sta (RecvBuf),y ; Store received character
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lda #$0F
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sta IndReg ; Restore indirect segment
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inc RecvTail
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dec RecvFreeCnt
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cpx #33 ; check for buffer space low
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bcs @L9
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; Assert flow control
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@L2: lda RtsOff ; assert flow control if buffer space too low
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ldy #RegCommand
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sta (acia),y
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sta Stopped
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rts
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; Drop this char
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@L3: inc DropCnt+0 ;not time-critical
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bne @L9
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inc DropCnt+1
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bne @L9
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inc DropCnt+2
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bne @L9
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inc DropCnt+3
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@L9: rts
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;----------------------------------------------------------------------------
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;
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; CheckInitialized - internal check if initialized
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; Set carry and an error code if not initialized, clear carry and do not
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; change any registers if initialized.
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;
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CheckInitialized:
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bit Initialized
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bmi @L1
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lda #ErrNotInitialized
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ldx #0
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sec
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rts
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@L1: clc
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rts
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;----------------------------------------------------------------------------
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; Try to send a byte. Internal routine. A = TryHard
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TryToSend:
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sta tmp1 ; Remember tryHard flag
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ldx IndReg ; Save indirect segment
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lda #$0F
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sta IndReg ; Set system segment as indirect segment
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@L0: lda SendFreeCnt
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cmp #$ff
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beq @L3 ; Bail out
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; Check for flow stopped
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@L1: lda Stopped
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bne @L3 ; Bail out
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; Check that the UART is ready to send
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@L2: ldy #RegStatus
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lda (acia),y
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and #$10
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bne @L4
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bit tmp1 ; Keep trying if must try hard
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bmi @L0
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@L3: stx IndReg ; Restore indirect segment
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rts
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; Send byte and try again
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@L4: lda #BufferSeg
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sta IndReg
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ldy SendHead
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lda (SendBuf),y
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ldy #$0F
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sty IndReg
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ldy #RegData
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sta (acia),y
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inc SendHead
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inc SendFreeCnt
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jmp @L0
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;----------------------------------------------------------------------------
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;
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; PollReceive - poll for rx char
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; This function is useful in odd cases where the 6551 has a character in
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; it but it fails to raise an NMI. It might be edge-triggering conditions?
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; Actually, I'm not entirely sure that this condition can still arrise, but
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; calling this function does no harm.
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;
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PollReceive:
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ldx IndReg ; Save indirect segment
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lda #$0F
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sta IndReg ; Set system bank as indirect segment
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ldy #RegStatus
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lda (acia),y
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and #$08
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beq @L9
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lda (acia),y ; Read a second time? ###
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and #$08
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beq @L9
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ldy #RegData
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lda (acia),y
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ldy RecvFreeCnt
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beq @L9
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ldy #BufferSeg
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sty IndReg
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ldy RecvTail
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sta (RecvBuf),y
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inc RecvTail
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dec RecvFreeCnt
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@L9: stx IndReg ; Restore indirect segment
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rts
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;----------------------------------------------------------------------------
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;
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; DelayMs : delay for given number of milliseconds
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; This implementation isn't very rigerous; it merely delays for the
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; approximate number of clock cycles for the processor speed.
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; Algorithm:
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; repeat for number of milliseconds:
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; repeat for number of MHz of cpu speed:
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; delay for 1017 clock cycles
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;
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DelayMs: ;( .A=milliseconds )
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@L1: ldy #1 ; 1MHz
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@L2: ldx #203 ;(2)
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@L3: dex ;(2)
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bne @L3 ;(3) // 1017 cycles
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|
dey
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|
bne @L2
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|
sec
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|
sbc #1
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bne @L1
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|
rts
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.end
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