Dudes:

As you know, I usually pose a programming challenge around this time
of year... The prize is a free beer (or other beverage of your
choice) at the Embedded Systems Conference.

Here's this year's challenge:

    Write a routine to multiply two numbers, each in the range
    0-100... The numbers are in two registers, called SMALL and
    LARGE, and your 16-bit result should be in two different
    registers, called PROD_HI and PROD_LO.

    To make it easy on you, the SMALL number is guaranteed to be less
    than or equal to LARGE.  If it helps, you can assume that either
    both numbers will be odd or both will be even.

    Your routine may corrupt the SMALL and LARGE registers, and it
    may use as many registers as you like... The only restriction is
    that the entire routine must fit in 256 bytes and be executable
    on a 12-bit PIC (16C5x or 12C50x).

    You may assume that your routine is ORGed at address 0 and that
    it's NOT called as a subroutine, so you can feel free to use
    both levels of the stack.

    Entries will be judged on speed of execution only; ties will be
    broken by (in this order):

        Lack of restrictions (i.e., ability to multiply an odd by an
        even number, or insensitivity to SMALL being larger than
        LARGE),

        Code size,

        Number of registers used.

I just wrote one that takes 34 cycles... I'm SURE someone can do
better.

-Andy

P.S.  As always, the prize is non-transferable and has no cash value;
      if you win and aren't going to be at the Embedded Systems
      Conference, I'll just drink your beer for you.

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

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