Utility routines: SWAPPZERO

       Name: SWAPPZERO                                               [Show more]
       Type: Subroutine
   Category: Utility routines
    Summary: An unused routine that swaps bytes in and out of zero page
    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file


.SWAPPZERO

 LDX #K3+1              ; This routine starts copying zero page from the byte
                        ; after K3 and up, using X as an index

.SWPZL

 LDA ZP,X               ; These instructions have no effect, as they simply swap
 LDY ZP,X               ; a byte with itself
 STA ZP,X
 STY ZP,X

 INX                    ; Increment the loop counter

 BNE SWPZL              ; Loop back for the next byte

 RTS                    ; Return from the subroutine