Multiplication and division in assemly

glentech

Can someone give a sample routine for multiplication and division in assemly?· I tried the routine in the tv routine with·some modifications. (starting at the div[noparse]:)[/noparse] with no success.· I just want to divide a cnt number by 8000 for tenths of ms without using too many clock cycles.

Mike Green

Have a look at the Propeller Guts document here: http://forums.parallax.com/showthread.php?p=572669

This includes multiplication and division routines and some discussion of this.

glentech

Thanks mike I didnt know where to look.

Tracy Allen

Also, to multiply times a constant fraction like 1/8000, the calculation can be streamlined for speed.

1/8000 = 0.512 / 4096

0.512 = %0.10000011000100100110 to 20 places

There are tricks like Booth's algorithm where bit sequences like this, 11111, in a multiplier, can be simplified to 100000 minus 1. There was a discussion that when pretty deep into this kind of thing in:
Derivation of Algorithms for Multiplication by a Constant Fraction

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Tracy Allen
www.emesystems.com