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474 lines
12 KiB
ArmAsm
474 lines
12 KiB
ArmAsm
;
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; Serial driver for the C64 using a Swiftlink or Turbo-232 cartridge.
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;
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; Ullrich von Bassewitz, 2003-04-18
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;
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; The driver is based on the cc65 rs232 module, which in turn is based on
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; Craig Bruce device driver for the Switftlink/Turbo-232.
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;
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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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.include "zeropage.inc"
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.include "ser-kernel.inc"
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.include "ser-error.inc"
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.include "c64.inc"
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; ------------------------------------------------------------------------
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; Header. Includes jump table
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.segment "JUMPTABLE"
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; Driver signature
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.byte $73, $65, $72 ; "ser"
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.byte SER_API_VERSION ; Serial API version number
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; Jump table.
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.word INSTALL
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.word UNINSTALL
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.word OPEN
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.word CLOSE
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.word GET
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.word PUT
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.word STATUS
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.word IOCTL
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.word IRQ
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;----------------------------------------------------------------------------
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; I/O definitions
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ACIA = $DE00
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ACIA_DATA = ACIA+0 ; Data register
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ACIA_STATUS = ACIA+1 ; Status register
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ACIA_CMD = ACIA+2 ; Command register
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ACIA_CTRL = ACIA+3 ; Control register
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;----------------------------------------------------------------------------
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;
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; Global variables
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;
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; We reuse the RS232 zero page variables for the driver, since the ROM
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; routines cannot be used together with this driver.
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RecvHead = $B5 ; Head of receive buffer
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RecvTail = $BD ; Tail of receive buffer
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RecvFreeCnt = $F7 ; Number of bytes in receive buffer
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SendHead = $F8 ; Head of send buffer
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SendTail = $F9 ; Tail of send buffer
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SendFreeCnt = $FA ; Number of bytes free in send buffer
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.bss
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Stopped: .res 1 ; Flow-stopped flag
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RtsOff: .res 1 ;
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; Send and receive buffers: 256 bytes each
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RecvBuf: .res 256
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SendBuf: .res 256
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.data
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NmiContinue: .byte $4c ; JMP instruction for NMI save -- continue
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NmiSave: .res 2 ; normal NMI handler
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.rodata
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; Tables used to translate RS232 params into register values
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BaudTable: ; bit7 = 1 means setting is invalid
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.byte $FF ; SER_BAUD_45_5
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.byte $FF ; SER_BAUD_50
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.byte $FF ; SER_BAUD_75
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.byte $FF ; SER_BAUD_110
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.byte $FF ; SER_BAUD_134_5
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.byte $02 ; SER_BAUD_150
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.byte $05 ; SER_BAUD_300
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.byte $06 ; SER_BAUD_600
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.byte $07 ; SER_BAUD_1200
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.byte $FF ; SER_BAUD_1800
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.byte $08 ; SER_BAUD_2400
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.byte $09 ; SER_BAUD_3600
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.byte $0A ; SER_BAUD_4800
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.byte $0B ; SER_BAUD_7200
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.byte $0C ; SER_BAUD_9600
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.byte $0E ; SER_BAUD_19200
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.byte $0F ; SER_BAUD_38400
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.byte $FF ; SER_BAUD_57600
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.byte $FF ; SER_BAUD_115200
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.byte $FF ; SER_BAUD_230400
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BitTable:
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.byte $60 ; SER_BITS_5
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.byte $40 ; SER_BITS_6
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.byte $20 ; SER_BITS_7
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.byte $00 ; SER_BITS_8
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StopTable:
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.byte $00 ; SER_STOP_1
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.byte $80 ; SER_STOP_2
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ParityTable:
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.byte $00 ; SER_PAR_NONE
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.byte $20 ; SER_PAR_ODD
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.byte $60 ; SER_PAR_EVEN
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.byte $A0 ; SER_PAR_MARK
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.byte $E0 ; SER_PAR_SPACE
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.code
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;----------------------------------------------------------------------------
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; INSTALL routine. Is called after the driver is loaded into memory. If
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; possible, check if the hardware is present.
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; Must return an SER_ERR_xx code in a/x.
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INSTALL:
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; Deactivate DTR and disable 6551 interrupts
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lda #%00001010
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sta ACIA_CMD
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; Set up the nmi vector
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lda NMIVec
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ldy NMIVec+1
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sta NmiSave+0
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sty NmiSave+1
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lda #<NmiHandler
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ldy #>NmiHandler
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SetNMI: sta NMIVec
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sty NMIVec+1
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; Done, return an error code
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lda #<SER_ERR_OK
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tax ; A is zero
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rts
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;----------------------------------------------------------------------------
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; UNINSTALL routine. Is called before the driver is removed from memory.
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; Must return an SER_ERR_xx code in a/x.
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UNINSTALL:
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; Stop interrupts, drop DTR
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lda #%00001010
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sta ACIA_CMD
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; Restore NMI vector and return OK
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lda NmiSave+0
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ldy NmiSave+1
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jmp SetNMI
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;----------------------------------------------------------------------------
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; PARAMS routine. A pointer to a ser_params structure is passed in ptr1.
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; Must return an SER_ERR_xx code in a/x.
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OPEN:
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; Check if the handshake setting is valid
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ldy #SER_PARAMS::HANDSHAKE ; Handshake
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lda (ptr1),y
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cmp #SER_HS_HW ; This is all we support
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bne InvParam
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; Initialize buffers
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jsr InitBuffers
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; Set the value for the control register, which contains stop bits, word
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; length and the baud rate.
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ldy #SER_PARAMS::BAUDRATE
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lda (ptr1),y ; Baudrate index
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tay
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lda BaudTable,y ; Get 6551 value
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bmi InvBaud ; Branch if rate not supported
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sta tmp1
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ldy #SER_PARAMS::DATABITS ; Databits
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lda (ptr1),y
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tay
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lda BitTable,y
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ora tmp1
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sta tmp1
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ldy #SER_PARAMS::STOPBITS ; Stopbits
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lda (ptr1),y
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tay
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lda StopTable,y
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ora tmp1
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ora #%00010000 ; Receiver clock source = baudrate
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sta ACIA_CTRL
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; Set the value for the command register. We remember the base value in
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; RtsOff, since we will have to manipulate ACIA_CMD often.
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ldy #SER_PARAMS::PARITY ; Parity
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lda (ptr1),y
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tay
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lda ParityTable,y
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ora #%00000001 ; DTR active
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sta RtsOff
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ora #%00001000 ; Enable receive interrupts
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sta ACIA_CMD
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; Done
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lda #<SER_ERR_OK
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tax ; A is zero
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rts
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; Invalid parameter
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InvParam:
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lda #<SER_ERR_INIT_FAILED
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ldx #>SER_ERR_INIT_FAILED
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rts
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; Baud rate not available
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InvBaud:
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lda #<SER_ERR_BAUD_UNAVAIL
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ldx #>SER_ERR_BAUD_UNAVAIL
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rts
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;----------------------------------------------------------------------------
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; CLOSE: Close the port, disable interrupts and flush the buffer. Called
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; without parameters. Must return an error code in a/x.
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;
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CLOSE:
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; Stop interrupts, drop DTR
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lda #%00001010
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sta ACIA_CMD
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; Initalize buffers. Returns zero in a
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jsr InitBuffers
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; Return OK
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lda #<SER_ERR_OK
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tax ; A is zero
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rts
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;----------------------------------------------------------------------------
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; GET: Will fetch a character from the receive buffer and store it into the
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; variable pointer to by ptr1. If no data is available, SER_ERR_NO_DATA is
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; return.
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;
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GET: ldx SendFreeCnt ; Send data if necessary
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inx ; X == $FF?
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beq @L1
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lda #$00
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jsr TryToSend
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; Check for buffer empty
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@L1: lda RecvFreeCnt ; (25)
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cmp #$ff
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bne @L2
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lda #<SER_ERR_NO_DATA
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ldx #>SER_ERR_NO_DATA
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rts
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; Check for flow stopped & enough free: release flow control
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@L2: ldx Stopped ; (34)
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beq @L3
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cmp #63
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bcc @L3
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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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sta ACIA_CMD
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; Get byte from buffer
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@L3: ldx RecvHead ; (41)
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lda RecvBuf,x
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inc RecvHead
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inc RecvFreeCnt
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ldx #$00 ; (59)
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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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; PUT: Output character in A.
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; Must return an error code in a/x.
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;
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PUT:
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; Try to send
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ldx SendFreeCnt
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inx ; X = $ff?
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beq @L2
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pha
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lda #$00
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jsr TryToSend
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pla
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; Put byte into send buffer & send
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@L2: ldx SendFreeCnt
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bne @L3
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lda #<SER_ERR_OVERFLOW ; X is already zero
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rts
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@L3: ldx SendTail
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sta SendBuf,x
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inc SendTail
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dec SendFreeCnt
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lda #$ff
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jsr TryToSend
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lda #<SER_ERR_OK
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tax
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rts
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;----------------------------------------------------------------------------
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; STATUS: Return the status in the variable pointed to by ptr1.
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; Must return an error code in a/x.
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;
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STATUS: lda ACIA_STATUS
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ldx #0
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sta (ptr1,x)
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txa ; SER_ERR_OK
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rts
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;----------------------------------------------------------------------------
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; IOCTL: Driver defined entry point. The wrapper will pass a pointer to ioctl
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; specific data in ptr1, and the ioctl code in A.
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; Must return an error code in a/x.
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;
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IOCTL: lda #<SER_ERR_INV_IOCTL ; We don't support ioclts for now
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ldx #>SER_ERR_INV_IOCTL
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rts
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;----------------------------------------------------------------------------
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; IRQ: Not used on the C64
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;
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IRQ = $0000
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;----------------------------------------------------------------------------
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;
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; NMI handler
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; C128 NMI overhead=76 cycles: int=7, maxLatency=6, ROMenter=33, ROMexit=30
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; C64 NMI overhead=76 cycles: int=7, maxLatency=6, ROMenter=34, ROMexit=29
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;
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; timing: normal=76+43+9=128 cycles, assertFlow=76+52+9=137 cycles
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;
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; C128 @ 115.2k: 177 cycles avail (fast)
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; C64 @ 57.6k: 177 cycles avail, worstAvail=177-43? = 134
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; SCPU @ 230.4k: 868 cycles avail: for a joke!
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;
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NmiHandler:
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pha
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lda ACIA_STATUS ;(4) ;status ;check for byte received
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and #$08 ;(2)
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beq @L9 ;(2*)
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cld
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txa
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pha
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tya
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pha
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@L1: lda ACIA_DATA ;(4) data ;get byte and put into receive buffer
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ldy RecvTail ;(4)
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ldx RecvFreeCnt ;(4)
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beq @L3 ;(2*) Jump if no space in receive buffer
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sta RecvBuf,y ;(5)
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inc RecvTail ;(6)
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dec RecvFreeCnt ;(6)
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cpx #33 ;(2) check for buffer space low
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bcc @L2 ;(2*)
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jmp NMIEXIT ;(3)
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; Assert flow control
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@L2: lda RtsOff ;(3) assert flow control if buffer space too low
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sta ACIA_CMD ;(4) command
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sta Stopped ;(3)
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@L3: jmp NMIEXIT ;(3)
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@L9: pla
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jmp NmiContinue
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;----------------------------------------------------------------------------
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; Try to send a byte. Internal routine. A = TryHard
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.proc TryToSend
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sta tmp1 ; Remember tryHard flag
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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 swiftlink is ready to send
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@L2: lda ACIA_STATUS
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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: rts
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; Send byte and try again
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@L4: ldx SendHead
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lda SendBuf,x
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sta ACIA_DATA
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inc SendHead
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inc SendFreeCnt
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jmp @L0
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.endproc
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;----------------------------------------------------------------------------
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; Initialize buffers
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InitBuffers:
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ldx #0
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stx Stopped
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stx RecvHead
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stx RecvTail
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stx SendHead
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stx SendTail
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dex ; X = 255
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stx RecvFreeCnt
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stx SendFreeCnt
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rts
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