mirror of
https://github.com/tjboldt/Apple2-IO-RPi.git
synced 2024-11-22 02:30:46 +00:00
210 lines
3.8 KiB
NASM
210 lines
3.8 KiB
NASM
; Copyright Terence J. Boldt (c)2020-2023
|
|
; 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 firmware
|
|
; that allows the Apple II to boot from the card
|
|
; and for ProDOS to recognize the card as two
|
|
; hard drivers
|
|
|
|
;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
|
|
MenuCommand = $08
|
|
|
|
.org SLOT*$100 + $C000
|
|
;ID bytes for booting and drive detection
|
|
cpx #$20 ;ID bytes for ProDOS and the
|
|
cpx #$00 ; Apple Autostart ROM
|
|
cpx #$03 ;
|
|
|
|
ldx #SLOT*$10
|
|
stx $2b
|
|
stx Unit
|
|
|
|
;force EPROM to second page on boot
|
|
lda #$3f ;set all flags high and page 3 of EPROM for menu
|
|
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 Driver
|
|
|
|
;load first two blocks and execute to boot
|
|
Start:
|
|
lda #$01 ;set read command
|
|
sta Command
|
|
|
|
lda #$00 ;block 0
|
|
sta BlockLo
|
|
sta BlockHi
|
|
sta BufferLo ;buffer at $800
|
|
lda #$08
|
|
sta BufferHi
|
|
jsr Driver ;get the block
|
|
|
|
jmp $801 ;execute the block
|
|
|
|
; ProDOS Driver code
|
|
; First check that this is the right drive
|
|
Driver:
|
|
ldx Unit
|
|
lda Command; Check which command is being requested
|
|
beq GetStatus ;0 = Status command
|
|
cmp #ReadBlockCommand
|
|
beq ReadBlockAndSetTime
|
|
cmp #WriteBlockCommand
|
|
beq WriteBlock
|
|
sec ;set carry as we don't support any other commands
|
|
lda #$53 ;Invalid parameter error
|
|
rts
|
|
|
|
; ProDOS Status Command Handler
|
|
GetStatus:
|
|
ldx #$ff ;low byte number of blocks
|
|
ldy #$ff ;high byte number of blocks
|
|
lda #$0 ;zero accumulator and clear carry for success
|
|
clc
|
|
rts
|
|
|
|
; ProDOS Read Block Command
|
|
ReadBlockAndSetTime:
|
|
lda BlockHi ; only get the time if block 0002
|
|
bne readBlock
|
|
lda BlockLo
|
|
cmp #$02
|
|
bne readBlock
|
|
ldy #$00 ;Get the current time on each block read for now
|
|
lda #GetTimeCommand
|
|
jsr SendByte
|
|
getTimeByte:
|
|
jsr GetByte
|
|
sta $bf90,y
|
|
iny
|
|
cpy #$04
|
|
bne getTimeByte
|
|
readBlock:
|
|
lda #ReadBlockCommand ;read the block after setting the clock
|
|
jsr SendByte
|
|
lda BlockLo
|
|
jsr SendByte
|
|
lda BlockHi
|
|
jsr SendByte
|
|
txa
|
|
jsr SendByte
|
|
ldy #$0
|
|
jsr read256
|
|
inc BufferHi
|
|
jsr read256
|
|
dec BufferHi
|
|
lda #$0 ;zero accumulator and clear carry for success
|
|
clc
|
|
rts
|
|
|
|
read256:
|
|
jsr GetByte
|
|
sta (BufferLo),y
|
|
iny
|
|
bne read256
|
|
rts
|
|
|
|
; ProDOS Write Block Command
|
|
WriteBlock:
|
|
lda #WriteBlockCommand
|
|
jsr SendByte
|
|
lda BlockLo
|
|
jsr SendByte
|
|
lda BlockHi
|
|
jsr SendByte
|
|
txa
|
|
jsr SendByte
|
|
ldy #$0
|
|
jsr write256
|
|
inc BufferHi
|
|
jsr write256
|
|
dec BufferHi
|
|
lda #$0 ;zero accumulator and clear carry for success
|
|
clc
|
|
rts
|
|
|
|
write256:
|
|
lda (BufferLo),y
|
|
jsr SendByte
|
|
iny
|
|
bne write256
|
|
rts
|
|
|
|
SendByte:
|
|
pha
|
|
waitWrite:
|
|
lda InputFlags
|
|
rol
|
|
rol
|
|
bcs waitWrite
|
|
pla
|
|
sta OutputByte
|
|
lda #$0e ; set bit 0 low to indicate write started
|
|
sta OutputFlags
|
|
finishWrite:
|
|
lda InputFlags
|
|
rol
|
|
rol
|
|
bcc finishWrite
|
|
lda #$0f
|
|
sta OutputFlags
|
|
rts
|
|
|
|
GetByte:
|
|
lda #$0d ;set read flag low
|
|
sta OutputFlags
|
|
waitRead:
|
|
lda InputFlags
|
|
rol
|
|
bcs waitRead
|
|
lda InputByte
|
|
pha
|
|
lda #$0f ;set all flags high
|
|
sta OutputFlags
|
|
finishRead:
|
|
lda InputFlags
|
|
rol
|
|
bcc finishRead
|
|
pla
|
|
end:
|
|
rts
|
|
|
|
.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
|
|
|