On Sat, 30 Mar 2002, Giorgio De Nunzio wrote:

> Hi all!
> >From time to time this kind of questions are back...
> I need a good 24 bit Square root (binary restoring) routine for the 16f84.
> I have seen the one at
> http://www.piclist.com/techref/microchip/math/sqrt/sqrt24.htm but it is
> for the 17c43 and contains an instruction I am not understanding: movfp.
> The other instructions are easily understandable even if I do not know the
> 17c43.
> Can someone help, with a specific 16f84 routine or simply by explaining to
> me what that instructions is used for, so that I can translate it in 16f84
> language?

Andy David (the author of the routine to which you refer), based his
algorithm on the 16-bit routine I wrote for the midrange family:

http://www.dattalo.com/technical/software/pic/picsqrt.html

You can get some idea on the general algorithm here:

http://www.dattalo.com/technical/theory/sqrt.html

I'd like to say that extending the 16-bit routine to 24 bits is straight
forward. Unfortunately, I don't like to lie. If I extended it, I'd
probably go to 32-bits and optimize when needed for 24-bits.

Oh, and of no use to you..., I finally linked in my 18cxxx 16-bit square
root routine:

http://www.dattalo.com/technical/software/pic/sqrt18.asm

It had been sitting on the server collecting dust.

Scott

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