Here is an 8 bit base 2 logarithm example.
http://www.interstice.com/%7esdattalo/technical/software/pic/piclog.html
It uses a 16 entries table and linear interpolation. The program can be
easily adapted for natural logarithm by changing values in the table.
Generally, if you want to find some other base logarithm having only one
logarithm routine, use the equation:

         log x
            a
log x = --------
   n     log n
            a

The same table-based technique will do the job for 16 bit numbers. The
best solution will depend on what accuracy do you need, how fast, and what
for.


Good luck
_

Nikolai Golovchenko, Electrical Engineering Student
National Mining University of Ukraine www.nmuu.dp.ua
Dnepropetrovsk, Ukraine
E-mail: golovchenko@mail.ru


-----Original Message-----
From: Andy Farrar <andrew.farrar@PORT.AC.UK>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Thursday, December 09, 1999 6:40 PM
Subject: natural logs


Hello,
I have a problem with  knowing where to start, has anybody got
example code or the method used in taking the natural log of an 8 bit
binary number, and preferably a 16 bit number.
Any help would be most appreciated.
Many thanks
Andrew Farrar