Apple2-IO-RPi/Apple2/CommandFirmware.asm
2021-10-26 23:13:06 -04:00

176 lines
2.9 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
MenuCommand = $08
InputString = $fd67
PrintChar = $fded
Keyboard = $c000
ClearKeyboard = $c010
Wait = $fca8
.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 #$05 ;execute command
jsr SendByte
ldy #$00
sendHelp:
lda HelpCommand,y
beq endSendHelp
jsr SendByte
iny
bne sendHelp
endSendHelp:
lda #$00
jsr SendByte
jsr DumpOutput
lda $33
pha
lda #$a4
sta $33
GetCommand:
jsr InputString
lda $0200
cmp #$8d ;skip when return found
beq GetCommand
jsr SendCommand
clc
bcc GetCommand
SendCommand:
bit ClearKeyboard
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
DumpOutput:
jsr GetByte
bcs skipOutput
cmp #$00
beq endOutput
jsr PrintChar
skipOutput:
bit Keyboard ;check for keypress
bpl DumpOutput ;keep dumping output if no keypress
lda Keyboard ;send keypress to RPi
jsr PrintChar
and #$7f
jsr SendByte
bit ClearKeyboard
clc
bcc DumpOutput
endOutput:
rts
HelpCommand:
.byte "a2help",$00
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
bcc readByte
bit Keyboard ;keypress will abort waiting to read
bpl waitRead
lda #$1f ;set all flags high and exit
sta OutputFlags
sec ;failure
rts
readByte:
lda InputByte
pha
lda #$1f ;set all flags high
sta OutputFlags
finishRead:
lda InputFlags
rol
bcc finishRead
pla
clc ;success
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