82 lines
2.0 KiB
NASM
82 lines
2.0 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 formerly contained the source for the
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; firmware that had a file access
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; but is now empty except required common bytes
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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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.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
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cpx #$00 ;
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cpx #$03 ;
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cpx #$3C ;ID byte for Autostart ROM
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lda #$3f ;set all flags high and page 3 of EPROM for menu
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jmp PageJump
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;The following bytes must exist in this location for Pascal communications
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;as they are standard pointers for entry points
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.byte CommInit&$00FF ;low byte of rts for init of Pascal comms
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.byte $43 ; low byte of read for Pascal comms
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.byte $49 ; low byte of write for Pascal comms
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.byte $4F ; low byte of rts for status of Pascal comms
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CommInit:
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lda #$0f ; set all flags high and page 0 for comm driver
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sta OutputFlags
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ldx #$00 ; set error code to 0 for success
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rts
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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=$0f
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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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jmp Start ; this is never called as the EPROM page changes
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;load first two blocks and execute to boot
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Start:
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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 23 ;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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