mirror of
https://github.com/tjboldt/Apple2-IO-RPi.git
synced 2024-11-22 02:30:46 +00:00
141 lines
2.4 KiB
NASM
141 lines
2.4 KiB
NASM
; Copyright Terence J. Boldt (c)2024
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; Use of this source code is governed by an MIT
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; license that can be found in the LICENSE file.
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; This file contains the source for the clock
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; driver for the Apple2-IO-RPi
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EnableWriteLang = $C08B
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DisableWriteLang = $C082
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ProdosJump = $BF06
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ProdosClockCode = $BF07
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ProdosMachineId = $BF98
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PrintChar = $FDED
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PrintHex = $FDE3
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PrintByte = $FDDA
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GetTimeCommand = $03
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.org $2000
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; Find Apple2-IO-RPi card
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ldx #$06
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ldy #$09
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CheckIdBytes:
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lda $C700,y ; !! Self modifying code
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cmp IdBytes,y
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bne NextCard
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dey
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bne CheckIdBytes
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jmp FoundCard
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NextCard:
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dec CheckIdBytes+2
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ldy #$09
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dex
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bne CheckIdBytes
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CardNotFound:
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ldy #$00
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PrintCardNotFound:
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lda TextCardNotFound,y
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beq Failed
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ora #$80
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jsr PrintChar
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iny
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bne PrintCardNotFound
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Failed:
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rts
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FoundCard:
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ldy #$00
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PrintCardFound:
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lda TextCardFound,y
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beq PrintCardNumber
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ora #$80
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jsr PrintChar
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iny
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bne PrintCardFound
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PrintCardNumber:
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inx
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txa
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jsr PrintHex
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lda #$8D
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jsr PrintChar
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; Change driver code to point to the card
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txa
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ora #$C0
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sta GetByte+2
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sta SendByte+2
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; Change destination to be ProDOS clock code location
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lda ProdosClockCode
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sta DriverDestination+1
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lda ProdosClockCode+1
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sta DriverDestination+2
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; Changing RTS to JMP enables clock driver
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lda #$4C ; jump instruction
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sta ProdosJump
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; Enable writing to language card RAM
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; by triggering switch twice
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lda EnableWriteLang
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lda EnableWriteLang
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; write driver code to language card RAM
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ldy #$00
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WriteDriver:
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lda Driver,y
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DriverDestination:
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sta $D742,y ; !! this address gets modified above
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iny
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cpy #EndDriver-Driver+2
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bne WriteDriver
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; Disable writing to language card RAM
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lda DisableWriteLang
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; Update ProDOS Machine ID to mark clock as enabled
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lda ProdosMachineId
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ora #$01
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sta ProdosMachineId
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ldy #$00
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PrintFinished:
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lda TextDriverInstalled,y
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beq Finished
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ora #$80
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jsr PrintChar
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iny
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bne PrintFinished
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Finished:
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rts
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IdBytes:
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.byte $E0,$20,$E0,$00,$E0,$03,$E0,$3C,$A9,$3F
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TextCardFound:
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.byte "Found Apple2-IO-RPi in slot ",$00
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TextCardNotFound:
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.byte "Apple2-IO-RPi not found",$8D,$00
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TextDriverInstalled:
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.byte "Apple2-IO-RPi Clock driver version 0001",$8D,$00
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Driver:
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lda #GetTimeCommand
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SendByte:
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jsr $C749 ; !! address gets modified on installation
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ldy #$00
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getTimeByte:
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GetByte:
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jsr $C743 ; !! address gets modified on installation
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sta $bf90,y
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iny
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cpy #$04
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bne getTimeByte
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EndDriver:
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rts
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