Hi Gary,

There are a number of multi-byte routines out there for the 8051. Phillips had one on their website for years. It took 12 bytes of direct RAM in the target chip, and assembled to about 500 bytes or so of code. Not particularly easy to use, but it works. I have shipped it in a bunch of products, and one of these days want to rewrite it for readability and to make it easier to use. I usually wind up writing things like 16-bit comparison routines from scratch every time I need one.

If you want a copy, i'll send one to you. What kind of math are you planning? This code deals with fixed point integer math. I have not found it necessary to use floating point for anything in 20 years or so of programming. Most of the stuff I do just doesn't need it. Fixed point integer math works well enough.

Anyway, good luck!

Forrest