There is a little math coprocessor chip that uses a SP1 (or something) 
interface.  That should simplify things somewhat.

Bill


----- Original Message ----- 
From: "life speed" <life_speed@yahoo.com>
To: <piclist@mit.edu>
Sent: Wednesday, November 02, 2005 3:37 PM
Subject: [PIC] 64 bit math fixed or floating point divide 48 bit multiply


>I need to improve on the speed of some
> arbitrary-precision division and multiplication
> routines written for the CCS (CCSinfo.com) compiler in
> C code for the PIC18F8722.
>
> I would like to find a 64/64 bit or 64/48 bit fixed or
> floating point division routine in assembly for the
> PIC.  I also require 48 bit multiplication.  So far I
> have not had much luck in my search.  Does anybody
> know if such a routine has been written?  I require a
> great deal of precision in my application.  I am a
> hardware engineer, assembly language is not my
> specialty, so I would prefer not to reinvent the wheel
> if possible.  The Matlab equations I must perform on
> the PIC are attached.
>
> Thanks,
>
> Clay
>
> format long;
> Fout = 12.1*10^9            % desired output freq
> FGHz = Fout/2;              % fundamental frequency
> before doubler
> Fref = 684.26*10^6; % nominal reference freq
> if FGHz < 6*10^9 % # of zeroed accumulator LSB's =
> nz = 8; % 8 for F < 6 GHz
> else %     7 for F >= 6 GHz
> nz = 7;
> end
> a = floor(2^20*(Fref/FGHz) + 0.5) % accumulator value
> seed1 = floor(a/2^nz)*2^nz; % accumulator with LSB's
> forced to zero
> dr1 = 2^20/seed1; % effective accumulator divide
> ratio
> Fref_act1 = FGHz/dr1; % exact reference frequency
> Fdds1 = (Fref_act1 - 600*10^6)*8 - 600*10^6; % exact
> DDS frequency
> if abs(Fdds1 - 66.66666*10^6) < 0.4 % reduce
> accumulator by 1 if DDS is close to 66.66666 MHz
> seed = floor(a/2^nz - 1)*2^nz
> dr = 2^20/seed
> Fref_act = FGHz/dr
> Fdds = (Fref_act1 - 600*10^6)*8 - 600*10^6
> else
> seed = seed1
> Fref_act = Fref_act1
> dr = dr1
> Fdds = Fdds1
> end
> DDS_bits = floor(2^48*(Fdds/(300*10^6)) + 0.5) % DDS
> command bits
>
>
>
>
> __________________________________
> Yahoo! FareChase: Search multiple travel sites in one click.
> http://farechase.yahoo.com
> -- 
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist 

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist