Apple2-IO-RPi/Apple2/RPi.Command.asm

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.ORG $300
INBUF = $200 ;GETLN input buffer.
WAIT = $FCA8 ;Monitor wait routine.
BELL = $FF3A ;Monitor bell routine.
EXTRNCMD = $BE06 ;External cmd JMP vector.
XTRNADDR = $BE50 ;Ext cmd implementation addr.
XLEN = $BE52 ;length of command string-1.
XCNUM = $BE53 ;CI cmd no. (ext cmd - 0).
PBITS = $BE54 ;Command parameter bits.
XRETURN = $BE9E ;Known RTS instruction.
InputByte = $c0fe
OutputByte = $c0fd
InputFlags = $c0fb
OutputFlags = $c0f7
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
;
; FIRST SAVE THE EXTERNAL COMMAND ADDRESS SO YOU WON'T
; DISCONNECT ANY PREVIOUSLY CONNECTED COMMAND.
;
LDA EXTRNCMD+1
STA NXTCMD
LDA EXTRNCMD+2
STA NXTCMD+1
;
LDA #<RPI ;Install the address of our
STA EXTRNCMD+1 ; command handler in the
LDA #>RPI ; external command JMP
STA EXTRNCMD+2 ; vector.
RTS
;
RPI: LDX #0 ;Check for our command.
NXTCHR: LDA INBUF,X ;Get first character.
ora #$20 ;Make it lower case
CMP CMD,X ;Does it match?
BNE NOTOURS ;No, back to CI.
INX ;Next character
CPX #CMDLEN ;All characters yet?
BNE NXTCHR ;No, read next one.
;
LDA #CMDLEN-1 ;Our cmd! Put cmd length-1
STA XLEN ; in CI global XLEN.
LDA #>XRETURN ;Point XTRNADDR to a known
STA XTRNADDR ; RTS since we'll handle
LDA #<XRETURN ; at the time we intercept
STA XTRNADDR+1 ; our command.
LDA #0 ;Mark the cmd number as
STA XCNUM ; zero (external).
STA PBITS ;And indicate no parameters
STA PBITS+1 ; to be parsed.
lda #$8d
jsr $fded
clc
bcc SendCommand
;
NOTOURS: SEC ; ALWAYS SET CARRY IF NOT YOUR
JMP (NXTCMD) ; CMD AND LET NEXT COMMAND TRY
; ; TO CLAIM IT.
SendCommand:
bit ClearKeyboard
lda #$05 ;send command 5 = exec
jsr SendByte
ldy #$03 ;skip over "RPI"
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:
clc
rts
;macro for string with high-bit set
.macro aschi str
.repeat .strlen (str), c
.byte .strat (str, c) | $80
.endrep
.endmacro
CMD: aschi "rpi"
CMDLEN = 3 ;Our command length
;
NXTCMD: .byte 0,0 ; STORE THE NEXT EXT CMD'S
; ADDRESS HERE.