>As a consequence B7 & B3 is untouched and there are only 3
swaps needed
        >making the code shorter.
        >Rewriting it for an 8 bit swap as required here, produces -
        >
        >        movwf   source
        >        btfsc   source,0
        >         xorlw  h'81'
        >        btfsc   source,7
        >         xorlw  h'81'
        >        btfsc   source,1
        >         xorlw  h'42'
        >        btfsc   source,6
        >         xorlw  h'42'
        >        btfsc   source,2
        >         xorlw  h'24'
        >        btfsc   source,5
        >         xorlw  h'24'
        >        btfsc   source,3
        >         xorlw  h'18'
        >        btfsc   source,4
        >         xorlw  h'18'
        >
        >17 instructions, time varies depending on data but fairly
quick.

        A minor point, possibly, but...

        Something that Andy Warren wrote a few years ago is that
        the path through a btfsc/s instruction is isochronous.
        Either the following instruction is executed, or it isn't,
        so the btfsc/s will either take two instruction cycles to
        execute the btfsc/s and the following instruction, or two
        instructions to execute the btfsc/s and the skip.

        Either way, the time from one btfsc/s to the next is always
        two cycles, making this routine isochronous.


- Andy.
---------------------------------------------------------
Andrew David, Software Manager, Ultronics Ltd, Cheltenham
akdavid@ultronics.co.uk          http://www.ultronics.com