Apple2-IO-RPi/Apple2/CommandFirmware.asm
2021-04-01 08:34:13 -04:00

133 lines
2.2 KiB
NASM

;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
.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=$2f
;entry points for ProDOS
DriverEntry:
lda #$0f ;set all flags high and page 0 of EPROM
sta OutputFlags
Start:
jsr $c300 ;enable 80 columns
lda $33
pha
lda #$a4
sta $33
GetCommand:
jsr $fd67
lda $0200
cmp #$8d ;skip when return found
beq GetCommand
jsr DumpOutput
clc
bcc GetCommand
DumpOutput:
lda #$05 ;send command 5 = exec
jsr SendByte
ldy #$00
getInput:
lda $0200,y
cmp #$8d
beq sendNullTerminator
and #$7f
jsr SendByte
iny
bne getInput
sendNullTerminator:
lda #$00
jsr SendByte
getOutput:
jsr GetByte
cmp #$00
beq endOutput
jsr $fded
clc
bcc getOutput
endOutput:
rts
SendByte:
pha
waitWrite:
lda InputFlags
rol
rol
bcs waitWrite
pla
sta OutputByte
lda #$1e ; set bit 0 low to indicate write started
sta OutputFlags
finishWrite:
lda InputFlags
rol
rol
bcc finishWrite
lda #$1f
sta OutputFlags
rts
GetByte:
lda #$1d ;set read flag low
sta OutputFlags
waitRead:
lda InputFlags
rol
bcs waitRead
lda InputByte
pha
lda #$1f ;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 7 ;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