Greg Young <PICLIST@MITVMA.MIT.EDU> wrote:

> I'm not even sure the posted version will work. It begins by
> performing a rotation, the results of which is checks for
> zero/non-zero. Yet, the initialize state of the carry (which is
> shifted in bit 7 of TEST) is unknown. If initially set, it would
> blow the algorithm (I think)...

    Greg:

    Yeah, you're right... Thanks for catching that.

    There should be a "CLRC" before the "RRF".  That'll teach me to
    write code online instead of pasting from my text editor, I
    guess.

> For more compact code, why not just add -3 until it overflows or
> zeroes. Something like (assuming a 14-bit core):
>
> Div3    MOVF    TEST,W          ; W = Value to Test (Set Z)
> :next   BTFSC   Z               ; If Z Set, Divisible by Zero
>         RETLW   1
>         ADDLW   -3              ; Check Next Iteration
>         BTFSC   C               ; Done if Overflow
>         goto    :next           ; Continue til Done
>         RETLW   0               ; Done
>

    As you obviously realize, your code won't work on a 12-bit PIC.

    Also, it's a lot slower than the "challenge" code, and it slows
    WAY down when it's scaled up to 16 bits.

    I guess I worded the challenge unclearly... I should have said:

        The challenge is to write a faster routine, or one which
        executes at essentially the same speed but is shorter.

    Thanks again for pointing out my error...

    -Andy

Andrew Warren - fastfwd@ix.netcom.com
Fast Forward Engineering, Vista, California
http://www.geocities.com/SiliconValley/2499