Apple2-IO-RPi/Apple2/Shell.asm
2022-02-23 22:42:19 -05:00

269 lines
3.7 KiB
NASM
Executable File

; Copyright Terence J. Boldt (c)2021-2022
; Use of this source code is governed by an MIT
; license that can be found in the LICENSE file.
; This file contains the source for the SHELL
; application that runs on the Apple II to talk
; to the Raspberry Pi
;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
InputByte = $c08e
OutputByte = $c08d
InputFlags = $c08b
OutputFlags = $c087
ResetCommand = $00
ReadBlockCommand = $01
WriteBlockCommand = $02
GetTimeCommand = $03
ChangeDriveCommand = $04
ExecCommand = $05
LoadFileCommand = $06
SaveFileCommand = $07
MenuCommand = $08
ShellCommand = $09
InputString = $fd6a
StringBuffer = $0200
PrintChar = $fded
Keyboard = $c000
ClearKeyboard = $c010
Home = $fc58
Wait = $fca8
PromptChar = $33
Read80Col = $c01f
TextPage1 = $c054
TextPage2 = $c055
htab = $24
vtab = $25
BasL = $28
htab80 = $057b
BasCalc = $fbc1
LastChar = $06
SlotL = $fe
SlotH = $ff
ESC = $9b
.org $2000
ldx #$07 ; start at slot 7
DetectSlot:
ldy #$00
lda #$fc
sta SlotL
txa
ora #$c0
sta SlotH
lda (SlotL),y
bne nextSlot
iny
lda (SlotL),y
bne nextSlot
iny
lda (SlotL),y
cmp #$17
bne nextSlot
iny
lda (SlotL),y
cmp #$14
bne nextSlot
txa
asl
asl
asl
asl
tax
clc
bcc Start
nextSlot:
dex
bne DetectSlot
rts
Start:
lda #$8d
jsr $c300 ; force 80 columns
lda LastChar
pha
bit ClearKeyboard
lda #ResetCommand
jsr SendByte
lda #ShellCommand
jsr SendByte
jsr DumpOutput
lda #ResetCommand
jsr SendByte
pla
sta LastChar
rts
DumpOutput:
jsr GetByte
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
jsr PrintChar
jsr SetCursor
jmp DumpOutput
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
SendByte:
pha
waitWrite:
lda InputFlags,x
rol
rol
bcs waitWrite
pla
sta OutputByte,x
lda #$1e ; set bit 0 low to indicate write started
sta OutputFlags,x
finishWrite:
lda InputFlags,x
rol
rol
bcc finishWrite
lda #$1f
sta OutputFlags,x
rts
GetByte:
lda #$1d ;set read flag low
sta OutputFlags,x
waitRead:
lda InputFlags,x
rol
bcc readByte
bit Keyboard ;keypress will abort waiting to read
bpl waitRead
keyPressed:
lda Keyboard ;send keypress to RPi
and #$7f
sta OutputByte,x
bit ClearKeyboard
lda #$1c ;set write flag low too
sta OutputFlags,x
finishKeyPress:
lda InputFlags,x
rol
rol
bcc finishKeyPress
lda #$1d ;set flags back for reading
sta OutputFlags,x
jmp waitRead
readByte:
lda InputByte,x
pha
lda #$1f ;set all flags high
sta OutputFlags,x
finishRead:
lda InputFlags,x
rol
bcc finishRead
pla
clc ;success
end:
rts
SetCursor:
lda htab80 ;get horizontal location / 2
lsr
tay
lda TextPage2
bcc setChar
lda TextPage1
setChar:
lda (BasL),y
sta LastChar ; save so ClearCursor will pick it up
cmp #$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