mirror of
https://github.com/tjboldt/Apple2-IO-RPi.git
synced 2024-11-25 21:33:15 +00:00
175 lines
2.7 KiB
NASM
175 lines
2.7 KiB
NASM
; ProDOS Global Page
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Device5S1 = $bf1a ;POINTER FOR SLOT 5 DRIVE 1 DRIVER
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DeviceCount = $bf31 ;DEVICE COUNT -1
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DeviceList = $bf32 ;DEVICE LIST
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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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SlotDrive = $50
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InputByte = $c0de
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OutputByte = $c0dd
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ReadBlockCommand = $01
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WriteBlockCommand = $02
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NibbleStorage = $1d
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.org $1000
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; Register the driver with ProDOS
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lda #<Driver
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sta Device5S1
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lda #>Driver
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sta Device5S1+1
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; Add the drive to the device list
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inc DeviceCount
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lda DeviceCount
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ldy #SlotDrive
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sta DeviceList,y
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rts
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; ProDOS Driver code
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; First check that this is the right drive
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Driver:
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lda Unit
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cmp #SlotDrive
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beq DoCommand ;correct device, so proceed
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sec ;set carry as ProDOS treats this as an error
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lda #NoDevice ;put the error code in accumulator for ProDOS
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rts
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; Check which command is being requested
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DoCommand:
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lda Command
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beq GetStatus ;0 = Status command
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cmp #ReadBlockCommand
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beq ReadBlock
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cmp #WriteBlockCommand
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beq WriteBlock
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sec ;set carry as we don't support any other commands
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lda #$53 ;Invalid parameter error
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rts
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; ProDOS Status Command Handler
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GetStatus:
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ldx #$ff ;low byte number of blocks
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ldy #$ff ;high byte number of blocks
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lda #$0 ;zero accumulator and clear carry for success
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clc
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rts
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; ProDOS Read Block Command
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ReadBlock:
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lda #ReadBlockCommand
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jsr SendByte
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lda BlockLo
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jsr SendByte
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lda BlockHi
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jsr SendByte
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ldy #$0
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jsr read256
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inc BufferHi
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jsr read256
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dec BufferHi
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lda #$0 ;zero accumulator and clear carry for success
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clc
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rts
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read256:
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jsr GetByte
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sta (BufferLo),y
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iny
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bne read256
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rts
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; ProDOS Write Block Command
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WriteBlock:
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lda #WriteBlockCommand
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jsr SendByte
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lda BlockLo
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jsr SendByte
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lda BlockHi
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jsr SendByte
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ldy #$0
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jsr write256
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inc BufferHi
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jsr write256
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dec BufferHi
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lda #$0 ;zero accumulator and clear carry for success
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clc
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rts
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write256:
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lda (BufferLo),y
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jsr SendByte
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iny
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bne write256
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rts
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SendByte:
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pha
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lsr
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lsr
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lsr
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lsr
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jsr SendNibble
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pla
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jsr SendNibble
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rts
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SendNibble:
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and #$0F
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ora #$70 ;Write bit low
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pha
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waitWrite:
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lda InputByte
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asl ;Second highest bit goes low when ready
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bmi waitWrite
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pla
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sta OutputByte
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finishWrite:
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lda InputByte
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asl
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bpl finishWrite
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lda #$FF
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sta OutputByte
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rts
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GetByte:
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jsr GetNibble
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asl
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asl
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asl
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asl
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sta NibbleStorage
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jsr GetNibble
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and #$0f
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ora NibbleStorage
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lda NibbleStorage
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rts
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GetNibble:
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lda #$b0 ;set read flag low
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sta OutputByte
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waitRead:
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lda InputByte
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bmi waitRead
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ora #$f0 ;set all flags high
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sta OutputByte
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pha
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finishRead:
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lda InputByte
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bpl finishRead
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pla
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rts
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