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⌂ ∞ ▽ Elite on the 6502

Version analysis of CLDELAY

This code appears in the following versions (click to see it in the source code):

Code variations between these versions are shown below.

       Name: CLDELAY
       Type: Subroutine
   Category: Utility routines
    Summary: Delay by iterating through 5 * 256 (1280) empty loops

Code variation 1 of 2A variation in the comments only

This variation is blank in the 6502 Second Processor version.

Master
 This routine is unused in this version of Elite (it is left over from the
 6502 Second Processor version).


.CLDELAY

Code variation 2 of 2Specific to an individual platform

Tap on a block to expand it, and tap it again to revert.

Master
6502SP
 RTS                    \ Return from the subroutine, as CLDELAY does nothing in
                        \ this version of Elite (it is left over from the 6502
                        \ Second Processor version)

 PHX                    \ Store A, X and Y on the stack
 PHY
 PHA

 LDY #5                 \ We are going to loop for 5 * 256 empty loops, so set a
                        \ counter in Y for the outer loop

 LDX #0                 \ And set a counter in X for the inner loop

.CLDEL1

 DEX                    \ Decrement the inner loop counter

 BNE CLDEL1             \ Loop back to CLDEL1 until the inner loop counter has
                        \ rolled around to 0 again

 DEY                    \ Decrement the outer loop counter

 BNE CLDEL1             \ Loop back to CLDEL1 until the outer loop counter has
                        \ reached 0

 PLA                    \ Retrieve A, X and Y from the stack
 PLY
 PLX

 RTS                    \ Return from the subroutine