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100 lines
2.8 KiB
Plaintext
100 lines
2.8 KiB
Plaintext
;c02 library stddef.h02 assembly language subroutines
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;Requires External Zero Page Variables
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;DSTLO, DSTHI, SRCLO, SRCHI
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;External Variables
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;TEMP0, TEMP1, TEMP2
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;Constant Definitions
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TRUE EQU $FF ;Returned for Success or Failure
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FALSE EQU $00 ;by some Library Routines
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;savdst() - Save Destination Pointer
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SAVDST: JSR GETDST ;Load Destination Pointer
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JMP SAVRXY ;Save X & Y Registers
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;savsrc() - Save Source Pointer
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SAVSRC: JSR GETSRC ;Load Destination Pointer
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JMP SAVRXY ;Save X & Y Registers
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;Save Registers
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SAVREG: STA TEMP0 ;Save Accumulater
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SAVRXY: STX TEMP1 ;Save X Index
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STY TEMP2 ;Save Y Index
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RTS
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;Restore Registers
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RESREG: LDA TEMP0 ;Load Accumlator
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RESRXY: LDX TEMP1 ;Load X Index
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LDY TEMP2 ;Load Y Index
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RTS
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;Set Destination Pointer to Source Pointer
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SETDSS: JSR GETSRC ;Get Destination Pointer
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JMP SETDST ;Store in Source Pointer
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;Restore Destination Pointer
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RESDST: JSR RESRXY ;Load Address and Drop into SETDST
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;Initialize Destination Pointer
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SETDST: STX DSTLO ;Store Destination Pointer
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STY DSTHI
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RTS
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;Restore Source Pointer
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RESSRC: JSR RESRXY ;Load Saved Address
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JMP SETSRC ;Set Source Pointer
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;Set Source Pointer to Destination Pointer
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SETSRD: JSR GETDST ;Get Destination Point and fall into SETSRC
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;Initialize Source Pointer and Index
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SETSRC: STX SRCLO ;Store Source Pointer
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STY SRCHI
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LDY #$00 ;Initialize Index Into String
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RTS
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;Retrieve Source String Pointer
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GETDST: LDX DSTLO
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LDY DSTHI
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RTS
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;Retrieve Source String Pointer
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GETSRC: LDX SRCLO
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LDY SRCHI
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RTS
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;Add Accumulator to Destination Address
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ADDDSA: TAX ;Move Accumulator to Argument LSB
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LDY #0 ;Clear Argument MSB
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;Add to Destination Address
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;Args: Y,X = MSB,LSB of Integer to Add
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;Affects: A,Y,X
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ADDDST: LDA #DSTLO ;Set Index to Destination Pointer
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BNE ADDZPW ;and Execute ADDZPW
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;Add Accumulator to Source Address
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ADDSRA: TAX ;Move Accumulator to Argument LSB
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LDY #0 ;Clear Argument MSB
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;Add to Source Address
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;Args: Y,X = MSB,LSB of Integer to Add
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;Affects: A,Y,X
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ADDSRC: LDA #SRCLO ;Set Index and Drop into ADDZPW
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;Add to Zero Page Word
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;Args: A = Address of Zero Page Word
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; Y,X = MSB,LSB of Integer to Add
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;Affects: A
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ADDZPW: STA TEMP3 ;Save Zero Page Address
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TXA ;Move Argument LSB to Accumulator
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LDX TEMP3 ;Set Index to Zero Page Address
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CLC ;Clear Carry
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ADC 0,X ;Add Argument LSB to Target LSB
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STA 0,X ;and Save Result
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TYA ;Move Argument MSB to Accumulator
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ADC 1,X ;Add Argument MSB to Target MSB
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STA 1,X ;and Save Result
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RTS
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