mirror of https://github.com/a2stuff/chtype.git
74 lines
2.9 KiB
ArmAsm
74 lines
2.9 KiB
ArmAsm
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;;;
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.org $2000
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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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VSLOT := $BE61 ;Verified slot parameter.
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;;;
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;;; REMEMBER TO SAVE THE PREVIOUS COMMAND ADDRESS.
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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 #>BEEPSLOT ;Install the address of our
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STA EXTRNCMD+1 ; command handler in the
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LDA #<BEEPSLOT ; external command JMP
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STA EXTRNCMD+2 ; vector.
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RTS
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;;;
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BEEPSLOT: LDX #0 ;Check for our command.
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NXTCHR: LDA INBUF,X ;Get first character.
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CMP CMD,X ;Does it match?
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BNE NOTOURS ;NO, SO CONTINUE WITH NEXT CMD.
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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 #>EXECUTE ;Point XTRNADDR to our
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STA XTRNADDR ; command execution
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LDA #<EXECUTE ; routine
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STA XTRNADDR+1
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LDA #0 ;Mark the cmd number as
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STA XCNUM ; zero (external).
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;;;
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LDA #%00010000 ;Set at least one bit
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STA PBITS ; in PBITS low byte!
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;;;
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LDA #%00000100 ;And mark PBITS high byte
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STA PBITS+1 ; that slot & drive are legal.
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CLC ;Everything is OK.
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RTS ;Return to BASIC.SYSTEM
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;;;
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EXECUTE: LDA VSLOT ;Get slot parameter.
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TAX ;Transfer to index reg.
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NXTBEEP: JSR BELL ;Else, beep once.
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LDA #$80 ;Set up the delay
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JSR WAIT ; and wait.
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DEX ;decrement index and
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BNE NXTBEEP ; repeat until x = 0.
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CLC ;All done successfully.
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RTS ;Back to BASIC.SYSTEM.
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;;;
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;;; IT'S NOT OUR COMMAND SO MAKE SURE YOU LET BASIC
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;;; CHECK WHETER OR NOT IT'S THE NEXT COMMAND.
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;;;
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NOTOURS: SEC ;SET CARRY AND LET
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JMP (NXTCMD) ; NEXT EXT CMD GO FOR IT.
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;;;
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CMD: .byte "BEEPSLOT" ;Our command
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CMDLEN = *-CMD ;Our command length
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NXTCMD: .word 0 ; STORE THE NEXT COMMAND'S
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; ADDRESS HERE.
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