Apple2-IO-RPi/Apple2/FileAccessFirmware.asm

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; Copyright Terence J. Boldt (c)2020-2024
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; Use of this source code is governed by an MIT
; license that can be found in the LICENSE file.
; This file formerly contained the source for the
; firmware that had a file access
; but is now empty except required common bytes
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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
InputByte = $c08e+SLOT*$10
OutputByte = $c08d+SLOT*$10
InputFlags = $c08b+SLOT*$10
OutputFlags = $c087+SLOT*$10
ReadBlockCommand = $01
WriteBlockCommand = $02
GetTimeCommand = $03
ChangeDriveCommand = $04
ExecCommand = $05
LoadFileCommand = $06
SaveFileCommand = $07
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MenuCommand = $08
.org SLOT*$100 + $C000
;ID bytes for booting and drive detection
cpx #$20 ;ID bytes for ProDOS
cpx #$00 ;
cpx #$03 ;
cpx #$3C ;ID byte for Autostart ROM
lda #$3f ;set all flags high and page 3 of EPROM for menu
jmp PageJump
;The following bytes must exist in this location for Pascal communications
;as they are standard pointers for entry points
.byte CommInit&$00FF ;low byte of rts for init of Pascal comms
.byte $43 ; low byte of read for Pascal comms
.byte $49 ; low byte of write for Pascal comms
.byte $4F ; low byte of rts for status of Pascal comms
CommInit:
lda #$0f ; set all flags high and page 0 for comm driver
sta OutputFlags
ldx #$00 ; set error code to 0 for success
rts
PageJump:
sta OutputFlags
jmp Start ;this jump is only called if coming in from PageJump with A=$0f
;entry points for ProDOS
DriverEntry:
lda #$0f ;set all flags high and page 0 of EPROM
sta OutputFlags
jmp Start ; this is never called as the EPROM page changes
;load first two blocks and execute to boot
Start:
end:
rts
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.repeat 251-<end
.byte 0
.endrepeat
.byte 0,0 ;0000 blocks = check status
.byte 23 ;bit set(0=status 1=read 2=write) unset(3=format, 4/5=number of volumes, 6=interruptable, 7=removable)
.byte DriverEntry&$00FF ;low byte of entry