mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2025-02-20 13:29:04 +00:00
48 lines
1.6 KiB
NASM
48 lines
1.6 KiB
NASM
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*``````````````````````````````*
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* DISKRW (NATHAN RIGGS) *
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* *
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* GENERAL PURPOSE ROUTINE FOR *
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* READING AND WRITING TO A *
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* *
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* INPUT: *
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* *
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* SLOT, DRIVE, VOLUME AND *
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* SECTOR, AS WELL AS READ OR *
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* WRITE FLAG, SHOULD BE SET *
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* BEFORE CALLING SUBROUTINE *
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* *
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* RETURN = BYTE TO WRITE, IF *
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* IN WRITE MODE *
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* *
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* OUTPUT: *
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* *
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* .A = ERROR CODE, IF ANY *
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* RETURN = BYTE RETURNED, IF *
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* IN READ MODE *
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* RETLEN = 1 *
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* *
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* DESTROY: AXYNVBDIZCMS *
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* ^^^^^ ^^^ *
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* *
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* CYCLES: 41+ *
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* SIZE: 34 BYTES *
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*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
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*
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DISKRW
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*
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:CLEAR
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LDA #00 ; CLEAR EXPECTED
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STA IOB_EVOL ; VOLUME BYTE
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LDA #1 ; BUFFER IS ALWAYS
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STA RETLEN ; A SINGLE BYTE
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LDA #>RETURN ; PASS BUFFER TO RWTS, WHICH
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LDY #<RETURN ; IS THE MOMLOC WHERE THE READ
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JSR RWTS ; OR WRITE DATA IS PASSED; CALL RWTS
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LDA #0 ; CLEAR .A TO INDICATE NO ERRORS
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BCC :EXIT ; IF CARRY IS CLEAR, NO ERRORS
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:ERR LDA IOB_ERR ; .A HOLDS ERROR CODE
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:EXIT
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LDX #00 ; CLEAR THE SCRATCH LOCATION
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STX $48 ; USED BY RWTS
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RTS
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