Apple2-IO-RPi/Apple2/Shell.asm

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NASM
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;ProDOS Zero Page
Command = $42 ;ProDOS Command
Unit = $43 ;ProDOS unit (SDDD0000)
BufferLo = $44
BufferHi = $45
BlockLo = $46
BlockHi = $47
; ProDOS Error Codes
IOError = $27
NoDevice = $28
WriteProtect = $2B
; hard code slot to 7 for now, will make it auto-detect later
SLOT = 7
InputByte = $c08e+SLOT*$10
OutputByte = $c08d+SLOT*$10
InputFlags = $c08b+SLOT*$10
OutputFlags = $c087+SLOT*$10
ResetCommand = $00
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ReadBlockCommand = $01
WriteBlockCommand = $02
GetTimeCommand = $03
ChangeDriveCommand = $04
ExecCommand = $05
LoadFileCommand = $06
SaveFileCommand = $07
MenuCommand = $08
ShellCommand = $09
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InputString = $fd6a
StringBuffer = $0200
PrintChar = $fded
Keyboard = $c000
ClearKeyboard = $c010
Home = $fc58
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Wait = $fca8
PromptChar = $33
Read80Col = $c01f
TextPage1 = $c054
TextPage2 = $c055
htab = $24
vtab = $25
BasL = $28
htab80 = $057b
BasCalc = $fbc1
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LastChar = $06
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ESC = $9b
.org $2000
Start:
jsr $c300 ; force 80 columns
lda LastChar
pha
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bit ClearKeyboard
lda #ResetCommand
jsr SendByte
lda #ShellCommand
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jsr SendByte
jsr DumpOutput
pla
sta LastChar
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rts
DumpOutput:
jsr GetByte
bcs checkInput
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cmp #$00
beq endOutput
pha
jsr ClearCursor
pla
cmp #'H'
beq setColumn
cmp #'V'
beq setRow
cmp #'C'
beq clearScreen
cmp #'T'
beq setTop
cmp #'B'
beq setBottom
cmp #'U'
beq moveUp
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jsr PrintChar
jsr SetCursor
jmp DumpOutput
checkInput:
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bit Keyboard ;check for keypress
bpl DumpOutput ;keep dumping output if no keypress
lda Keyboard ;send keypress to RPi
and #$7f
jsr SendByte
bit ClearKeyboard
jmp DumpOutput
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endOutput:
rts
clearScreen:
jsr Home
jsr SetCursor
jmp DumpOutput
setColumn:
jsr GetByte
sta htab
sta htab80
jsr SetCursor
jmp DumpOutput
setRow:
jsr GetByte
sta vtab
jsr BasCalc
jsr SetCursor
jmp DumpOutput
setTop:
jsr GetByte
sta $22
jmp DumpOutput
setBottom:
jsr GetByte
sta $23
jmp DumpOutput
moveUp:
dec vtab
lda vtab
jsr BasCalc
jsr SetCursor
jmp DumpOutput
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SendByte:
pha
waitWrite:
lda InputFlags
rol
rol
bcs waitWrite
pla
sta OutputByte
lda #$1e ; set bit 0 low to indicate write started
sta OutputFlags
finishWrite:
lda InputFlags
rol
rol
bcc finishWrite
lda #$1f
sta OutputFlags
rts
GetByte:
bit Keyboard ; skip byte read if key pressed
bcc keyPressed
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lda #$1d ;set read flag low
sta OutputFlags
waitRead:
lda InputFlags
rol
bcc readByte
bit Keyboard ;keypress will abort waiting to read
bpl waitRead
keyPressed:
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lda #$1f ;set all flags high and exit
sta OutputFlags
sec ;failure
rts
readByte:
lda InputByte
pha
lda #$1f ;set all flags high
sta OutputFlags
finishRead:
lda InputFlags
rol
bcc finishRead
pla
clc ;success
end:
rts
SetCursor:
lda htab80 ;get horizontal location / 2
lsr
tay
lda TextPage2
bcc setChar
lda TextPage1
setChar:
lda (BasL),y
sta LastChar ; save so ClearCursor will pick it up
cmp #$e0
bpl lowerCase
cmp #$c0
bpl upperCase
cmp #$a0
bpl symbol
cmp #$80
bpl noop
symbol:
lowerCase:
invert:
eor #$80
jmp storeChar
upperCase:
and #$1f
jmp storeChar
noop:
storeChar:
sta (BasL),y
lda TextPage1
rts
ClearCursor:
lda htab80 ;get horizontal location / 2
lsr
tay
lda TextPage2
bcc restoreChar
lda TextPage1
restoreChar:
lda LastChar
sta (BasL),y
lda TextPage1
rts