<fwd>
>I'm sure I saw an easy way to reverse a byte some time ago in
this list, but
>I've forgotten it..
>
>I want to change   b7 b6 b5 b4 b3 b2 b1 b0   to  b0 b1 b2 b3 b4
b5 b6 b7.
>
>Quickest & most code efficient??

Wagner's lookup table has to be about the quickest way... but something
a little more code efficient:

Enter with byte to be reversed in WREG, exits with reversed byte in
WREG. Reverse is trashed.


RevWReg:
rlcf WREG,f ; W   = d6 d5 d4 d3 d2 d1 d0 C
{C = d7}
rrcf Reverse,f ; Rev = d7 R7 R6 R5 R4 R3 R2 R1
{C = R0}
rlcf WREG,f ; W   = d5 d4 d3 d2 d1 d0 C  R0
{C = d6}
rrcf Reverse,f ; Rev = d6 d7 R7 R6 R5 R4 R3 R2
{C = R1}
rlcf WREG,f ; W   = d4 d3 d2 d1 d0 C  R0 R1
{C = d5}
rrcf Reverse,f ; Rev = d5 d6 d7 R7 R6 R5 R4 R3
{C = R2}
rlcf WREG,f ; W   = d3 d2 d1 d0 C  R0 R1 R2
{C = d4}
rrcf Reverse,f ; Rev = d4 d5 d6 d7 R7 R6 R5 R4
{C = R3}
rlcf WREG,f ; W   = d2 d1 d0 C  R0 R1 R2 R3
{C = d3}
rrcf Reverse,f ; Rev = d3 d4 d5 d6 d7 R7 R6 R5
{C = R4}
rlcf WREG,f ; W   = d1 d0 C  R0 R1 R2 R3 R4
{C = d2}
rrcf Reverse,f ; Rev = d2 d3 d4 d5 d6 d7 R7 R6
{C = R5}
rlcf WREG,f ; W   = d0 C  R0 R1 R2 R3 R4 R5
{C = d1}
rrcf Reverse,f ; Rev = d1 d2 d3 d4 d5 d6 d7 R7
{C = R6}
rlcf WREG,f ; W   = C  R0 R1 R2 R3 R4 R5 R6
{C = d0}
rrcf Reverse,w ; W   = d0 d1 d2 d3 d4 d5 d6 d7
{C = R7}

        return



- Andy.

---------------------------------------------------------
Andrew David, Software Manager, Ultronics Ltd, Cheltenham
akdavid@ultronics.co.uk          http://www.ultronics.com