"Chris Antos" <[EMAIL PROTECTED]> wrote:
> hm. i suppose i could do that. you have to be careful about division,
> though. i'm not sure about 68k series, but the x86 series does 64 bit
> division, but considers it an overflow if either the quotient or remainder
> exceeds 32bits (or maybe i'm even more dated than i realize - i'm going by
> the 386 reference, and maybe the Pentium has a way around this, i don't
> know).
The MC68000 (that's the CPU core at the heart of the MC68328) can do
only 32-bit multiplication and division. (Actually, it can multiply two
16-bit numbers giving a 32-bit result, and divide a 32-bit by a 16-bit,
giving 16-bit quotient and remainder.) Anything beyond that has to be
handled by some kind of library routine.
Writing a little routine to multiply two 32-bit values into a 64-bit
intermediate product, then dividing by a 32-bit scale factor, is a
technique I've used successfully on a couple of projects. I stole the
idea from Forth's */ operator.
--
Roger Chaplin
<[EMAIL PROTECTED]>
