183 lines
3.1 KiB
NASM
183 lines
3.1 KiB
NASM
; Copyright Terence J. Boldt (c)2020-2024
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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 firmware
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; that was formerly used to act as a pseudo-shell
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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+SLOT*$10
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OutputByte = $c08d+SLOT*$10
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InputFlags = $c08b+SLOT*$10
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OutputFlags = $c087+SLOT*$10
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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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InputString = $fd67
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PrintChar = $fded
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Keyboard = $c000
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ClearKeyboard = $c010
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Wait = $fca8
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.org SLOT*$100 + $C000
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;ID bytes for booting and drive detection
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cpx #$20 ;ID bytes for ProDOS and the
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cpx #$00 ; Apple Autostart ROM
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cpx #$03 ;
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ldx #SLOT*$10
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stx $2b
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stx Unit
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;force EPROM to second page on boot
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lda #$3f ;set all flags high and page 3 of EPROM for menu
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PageJump:
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sta OutputFlags
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jmp Start ;this jump is only called if coming in from PageJump with A=$2f
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;entry points for ProDOS
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DriverEntry:
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lda #$0f ;set all flags high and page 0 of EPROM
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sta OutputFlags
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Start:
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jsr $c300 ;enable 80 columns
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lda #$05 ;execute command
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jsr SendByte
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ldy #$00
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sendHelp:
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lda HelpCommand,y
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beq endSendHelp
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jsr SendByte
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iny
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bne sendHelp
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endSendHelp:
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lda #$00
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jsr SendByte
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jsr DumpOutput
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lda $33
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pha
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lda #$a4
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sta $33
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GetCommand:
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jsr InputString
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lda $0200
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cmp #$8d ;skip when return found
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beq GetCommand
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jsr SendCommand
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clc
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bcc GetCommand
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SendCommand:
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bit ClearKeyboard
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lda #$05 ;send command 5 = exec
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jsr SendByte
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ldy #$00
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getInput:
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lda $0200,y
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cmp #$8d
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beq sendNullTerminator
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and #$7f
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jsr SendByte
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iny
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bne getInput
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sendNullTerminator:
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lda #$00
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jsr SendByte
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DumpOutput:
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jsr GetByte
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bcs skipOutput
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cmp #$00
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beq endOutput
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jsr PrintChar
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skipOutput:
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bit Keyboard ;check for keypress
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bpl DumpOutput ;keep dumping output if no keypress
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lda Keyboard ;send keypress to RPi
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jsr PrintChar
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and #$7f
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jsr SendByte
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bit ClearKeyboard
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clc
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bcc DumpOutput
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endOutput:
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rts
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HelpCommand:
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.byte "a2help",$00
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SendByte:
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pha
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waitWrite:
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lda InputFlags
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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
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lda #$1e ; set bit 0 low to indicate write started
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sta OutputFlags
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finishWrite:
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lda InputFlags
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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
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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
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waitRead:
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lda InputFlags
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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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lda #$1f ;set all flags high and exit
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sta OutputFlags
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sec ;failure
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rts
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readByte:
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lda InputByte
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pha
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lda #$1f ;set all flags high
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sta OutputFlags
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finishRead:
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lda InputFlags
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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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.repeat 251-<end
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.byte 0
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.endrepeat
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.byte 0,0 ;0000 blocks = check status
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.byte 7 ;bit set(0=status 1=read 2=write) unset(3=format, 4/5=number of volumes, 6=interruptable, 7=removable)
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.byte DriverEntry&$00FF ;low byte of entry
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