forked from Apple-2-HW/Apple2-IO-RPi
174 lines
3.9 KiB
NASM
174 lines
3.9 KiB
NASM
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.ORG $300
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INBUF = $200 ;GETLN input buffer.
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WAIT = $FCA8 ;Monitor wait routine.
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BELL = $FF3A ;Monitor bell routine.
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EXTRNCMD = $BE06 ;External cmd JMP vector.
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XTRNADDR = $BE50 ;Ext cmd implementation addr.
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XLEN = $BE52 ;length of command string-1.
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XCNUM = $BE53 ;CI cmd no. (ext cmd - 0).
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PBITS = $BE54 ;Command parameter bits.
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XRETURN = $BE9E ;Known RTS instruction.
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InputByte = $c0fe
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OutputByte = $c0fd
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InputFlags = $c0fb
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OutputFlags = $c0f7
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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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InputString = $fd67
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PrintChar = $fded
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Keyboard = $c000
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ClearKeyboard = $c010
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Wait = $fca8
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;
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; FIRST SAVE THE EXTERNAL COMMAND ADDRESS SO YOU WON'T
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; DISCONNECT ANY PREVIOUSLY CONNECTED COMMAND.
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;
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LDA EXTRNCMD+1
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STA NXTCMD
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LDA EXTRNCMD+2
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STA NXTCMD+1
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;
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LDA #<RPI ;Install the address of our
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STA EXTRNCMD+1 ; command handler in the
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LDA #>RPI ; external command JMP
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STA EXTRNCMD+2 ; vector.
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RTS
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;
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RPI: LDX #0 ;Check for our command.
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NXTCHR: LDA INBUF,X ;Get first character.
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ora #$20 ;Make it lower case
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CMP CMD,X ;Does it match?
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BNE NOTOURS ;No, back to CI.
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INX ;Next character
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CPX #CMDLEN ;All characters yet?
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BNE NXTCHR ;No, read next one.
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;
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LDA #CMDLEN-1 ;Our cmd! Put cmd length-1
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STA XLEN ; in CI global XLEN.
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LDA #>XRETURN ;Point XTRNADDR to a known
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STA XTRNADDR ; RTS since we'll handle
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LDA #<XRETURN ; at the time we intercept
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STA XTRNADDR+1 ; our command.
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LDA #0 ;Mark the cmd number as
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STA XCNUM ; zero (external).
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STA PBITS ;And indicate no parameters
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STA PBITS+1 ; to be parsed.
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lda #$8d
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jsr $fded
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clc
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bcc SendCommand
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;
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NOTOURS: SEC ; ALWAYS SET CARRY IF NOT YOUR
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JMP (NXTCMD) ; CMD AND LET NEXT COMMAND TRY
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; ; TO CLAIM IT.
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SendCommand:
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bit ClearKeyboard
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lda #$05 ;send command 5 = exec
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jsr SendByte
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ldy #$03 ;skip over "RPI"
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getInput:
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lda $0200,y
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cmp #$8d
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beq sendNullTerminator
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and #$7f
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jsr SendByte
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iny
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bne getInput
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sendNullTerminator:
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lda #$00
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jsr SendByte
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DumpOutput:
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jsr GetByte
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bcs skipOutput
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cmp #$00
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beq endOutput
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jsr PrintChar
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skipOutput:
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bit Keyboard ;check for keypress
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bpl DumpOutput ;keep dumping output if no keypress
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lda Keyboard ;send keypress to RPi
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jsr PrintChar
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and #$7f
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jsr SendByte
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bit ClearKeyboard
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clc
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bcc DumpOutput
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endOutput:
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rts
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HelpCommand:
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.byte "a2help",$00
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SendByte:
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pha
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waitWrite:
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lda InputFlags
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rol
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rol
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bcs waitWrite
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pla
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sta OutputByte
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lda #$1e ; set bit 0 low to indicate write started
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sta OutputFlags
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finishWrite:
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lda InputFlags
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rol
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rol
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bcc finishWrite
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lda #$1f
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sta OutputFlags
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rts
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GetByte:
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lda #$1d ;set read flag low
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sta OutputFlags
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waitRead:
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lda InputFlags
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rol
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bcc readByte
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bit Keyboard ;keypress will abort waiting to read
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bpl waitRead
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lda #$1f ;set all flags high and exit
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sta OutputFlags
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sec ;failure
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rts
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readByte:
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lda InputByte
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pha
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lda #$1f ;set all flags high
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sta OutputFlags
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finishRead:
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lda InputFlags
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rol
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bcc finishRead
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pla
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clc ;success
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end:
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clc
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rts
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;macro for string with high-bit set
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.macro aschi str
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.repeat .strlen (str), c
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.byte .strat (str, c) | $80
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.endrep
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.endmacro
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CMD: aschi "rpi"
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CMDLEN = 3 ;Our command length
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;
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NXTCMD: .byte 0,0 ; STORE THE NEXT EXT CMD'S
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; ADDRESS HERE.
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