>
> > -----Original Message-----
> > From: M. Adam Davis [SMTP:adampic@UBASICS.COM]
> > Sent: Tuesday, June 10, 2003 3:59 AM
> > To:   PICLIST@MITVMA.MIT.EDU
> > Subject:      Re: [PIC]: brain teaser
> >
> > Does it beat all of the options here:
> >
> <http://www.piclist.com/techref/microchip/math/bit/revbits.htm>http://www.piclist.com/techref/microchip/math/bit/revbits.htm
> >
> > The fastest one takes 4 instruction cycles (lookup table).
> >
>I make that 8 cycles (REG being the randomly chosen register):
>
>         movf    REG,w           ; one cycle
>         call            reverse         ; two cycles
>         movwf   REG             ; one cycle
>
>reverse:
>         addwf   PCL,f           ; two cycles
>         retlw   0x00            ; two cycles
>         retlw   0x80
>         retlw   0x40
>
>Regards
>
>Mike

Now to the real world.  The above example assumes that:

1) The Addwf PCL,f  is one address location before a Mod 256 address.
2) That PCLATH is "magically" addressing the right 256 byte page
3) That the PIC involved is not a PIC18 core type.

Regards,

Jim

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