ON 20110426@10:00:52 AM at page:
On a web page you were interested in at:
http://www.piclist.com/Techref/microchip/math/bit/revbits.htm#40659.4172569444
Christopher Wall[CW-tekind-] Says

I think one correction needs to be made to the following "Middle" method by Dmitry A. Kiryashov. As it is right now, it doesn't work when both 'a' and 'h' are '1'.<br><br>
Example:<PRE>
;   instruction   X           W           CarryBit
                  1010 0011   xxxx xxxx   x
    swapf   X,W   1010 0011   0011 1010   x   
    xorwf   X,W   1010 0011   1001 1001   x
    andlw   0x66  1010 0011   0000 0000   x
    xorwf   X,F   1010 0011   0000 0000   x
    rrf     X,W   1010 0011   1101 0001   x
    rrf     X,F   1101 0001   1101 0001   x
    andlw   0x55  1101 0001   0101 0001   x
    addwf   X,F   0010 0010   0101 0001   1
    rrf     X,F   0001 0001   0101 0001   1
    addwf   X,F   0110 0010   0101 0001   1
    rlf     X,W   0110 0010   1100 0100   1
    rlf     X,F   1100 0100   1100 0100   1
</PRE> 0b11000100 is not the reverse of 0b10100011
By changing the last "rrf" instruction to a rrcf (rotate file right through carry) this now opperated correctly:
<PRE>;   instruction   X           W           CarryBit
                  1010 0011   xxxx xxxx   x
    swapf   X,W   1010 0011   0011 1010   x   
    xorwf   X,W   1010 0011   1001 1001   x
    andlw   0x66  1010 0011   0000 0000   x
    xorwf   X,F   1010 0011   0000 0000   x
    rrf     X,W   1010 0011   1101 0001   x
    rrf     X,F   1101 0001   1101 0001   x
    andlw   0x55  1101 0001   0101 0001   x
    addwf   X,F   0010 0010   0101 0001   1
    <u>rrcf</u>    X,F   1001 0001   0101 0001   0
    addwf   X,F   1110 0010   0101 0001   0
    rlf     X,W   1110 0010   1100 0101   0
    rlf     X,F   1100 0100   1100 0101   0
</PRE>

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