forked from Apple-2-HW/Apple2-IO-RPi
269 lines
3.7 KiB
NASM
Executable File
269 lines
3.7 KiB
NASM
Executable File
; Copyright Terence J. Boldt (c)2021-2022
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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 SHELL
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; application that runs on the Apple II to talk
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; to the Raspberry Pi
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;ProDOS Zero Page
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Command = $42 ;ProDOS Command
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Unit = $43 ;ProDOS unit (SDDD0000)
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BufferLo = $44
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BufferHi = $45
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BlockLo = $46
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BlockHi = $47
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; ProDOS Error Codes
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IOError = $27
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NoDevice = $28
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WriteProtect = $2B
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InputByte = $c08e
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OutputByte = $c08d
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InputFlags = $c08b
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OutputFlags = $c087
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ResetCommand = $00
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ReadBlockCommand = $01
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WriteBlockCommand = $02
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GetTimeCommand = $03
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ChangeDriveCommand = $04
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ExecCommand = $05
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LoadFileCommand = $06
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SaveFileCommand = $07
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MenuCommand = $08
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ShellCommand = $09
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InputString = $fd6a
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StringBuffer = $0200
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PrintChar = $fded
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Keyboard = $c000
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ClearKeyboard = $c010
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Home = $fc58
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Wait = $fca8
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PromptChar = $33
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Read80Col = $c01f
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TextPage1 = $c054
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TextPage2 = $c055
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htab = $24
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vtab = $25
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BasL = $28
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htab80 = $057b
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BasCalc = $fbc1
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LastChar = $06
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SlotL = $fe
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SlotH = $ff
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ESC = $9b
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.org $2000
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ldx #$07 ; start at slot 7
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DetectSlot:
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ldy #$00
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lda #$fc
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sta SlotL
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txa
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ora #$c0
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sta SlotH
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lda (SlotL),y
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bne nextSlot
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iny
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lda (SlotL),y
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bne nextSlot
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iny
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lda (SlotL),y
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cmp #$17
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bne nextSlot
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iny
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lda (SlotL),y
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cmp #$14
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bne nextSlot
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txa
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asl
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asl
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asl
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asl
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tax
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clc
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bcc Start
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nextSlot:
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dex
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bne DetectSlot
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rts
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Start:
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lda #$8d
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jsr $c300 ; force 80 columns
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lda LastChar
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pha
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bit ClearKeyboard
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lda #ResetCommand
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jsr SendByte
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lda #ShellCommand
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jsr SendByte
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jsr DumpOutput
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lda #ResetCommand
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jsr SendByte
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pla
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sta LastChar
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rts
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DumpOutput:
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jsr GetByte
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cmp #$00
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beq endOutput
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pha
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jsr ClearCursor
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pla
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cmp #'H'
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beq setColumn
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cmp #'V'
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beq setRow
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cmp #'C'
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beq clearScreen
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cmp #'T'
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beq setTop
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cmp #'B'
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beq setBottom
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cmp #'U'
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beq moveUp
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jsr PrintChar
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jsr SetCursor
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jmp DumpOutput
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endOutput:
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rts
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clearScreen:
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jsr Home
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jsr SetCursor
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jmp DumpOutput
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setColumn:
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jsr GetByte
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sta htab
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sta htab80
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jsr SetCursor
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jmp DumpOutput
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setRow:
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jsr GetByte
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sta vtab
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jsr BasCalc
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jsr SetCursor
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jmp DumpOutput
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setTop:
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jsr GetByte
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sta $22
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jmp DumpOutput
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setBottom:
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jsr GetByte
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sta $23
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jmp DumpOutput
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moveUp:
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dec vtab
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lda vtab
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jsr BasCalc
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jsr SetCursor
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jmp DumpOutput
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SendByte:
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pha
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waitWrite:
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lda InputFlags,x
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rol
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rol
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bcs waitWrite
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pla
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sta OutputByte,x
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lda #$1e ; set bit 0 low to indicate write started
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sta OutputFlags,x
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finishWrite:
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lda InputFlags,x
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rol
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rol
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bcc finishWrite
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lda #$1f
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sta OutputFlags,x
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rts
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GetByte:
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lda #$1d ;set read flag low
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sta OutputFlags,x
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waitRead:
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lda InputFlags,x
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rol
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bcc readByte
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bit Keyboard ;keypress will abort waiting to read
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bpl waitRead
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keyPressed:
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lda Keyboard ;send keypress to RPi
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and #$7f
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sta OutputByte,x
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bit ClearKeyboard
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lda #$1c ;set write flag low too
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sta OutputFlags,x
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finishKeyPress:
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lda InputFlags,x
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rol
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rol
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bcc finishKeyPress
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lda #$1d ;set flags back for reading
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sta OutputFlags,x
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jmp waitRead
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readByte:
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lda InputByte,x
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pha
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lda #$1f ;set all flags high
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sta OutputFlags,x
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finishRead:
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lda InputFlags,x
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rol
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bcc finishRead
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pla
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clc ;success
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end:
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rts
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SetCursor:
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lda htab80 ;get horizontal location / 2
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lsr
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tay
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lda TextPage2
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bcc setChar
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lda TextPage1
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setChar:
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lda (BasL),y
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sta LastChar ; save so ClearCursor will pick it up
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cmp #$e0
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bpl lowerCase
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cmp #$c0
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bpl upperCase
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cmp #$a0
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bpl symbol
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cmp #$80
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bpl noop
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symbol:
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lowerCase:
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invert:
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eor #$80
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jmp storeChar
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upperCase:
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and #$1f
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jmp storeChar
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noop:
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storeChar:
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sta (BasL),y
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lda TextPage1
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rts
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ClearCursor:
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lda htab80 ;get horizontal location / 2
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lsr
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tay
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lda TextPage2
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bcc restoreChar
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lda TextPage1
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restoreChar:
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lda LastChar
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sta (BasL),y
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lda TextPage1
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rts
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