Thanks to everyone for comments to date.
They have helped, I'm getting somewhere, but unfortunately not solved my immediate
problem.

Require to generate a CRC (non table driven)
for a PIC.  (non table driven as dont have spare ROM to store the table as what
most usual methods
employ.)
Other end of my link is another language.
(I will modify the (C) code (once I understand it) to suit.)

I have numerous code examples in C but no decent idiot proof explanations.
The confusion arises because of the slightly different implementations depending
on what flavour
of CRC you use.

The idea of a CRC I understand. (easy part)
Getting confused over the left (sometimes right)
shifting and reflecting, complementing of the
result that sometimes seems to happen to get
the "correct" resulting CRC.
Also the initial value of CRC whether start with
0000h or FFFFh
Help!

Anyone got any non-table driven known good code with explanation of the bit
shifting operations?

Thanks once again,
Bernard Wood
Hamilton
New Zealand

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