Dave Dribin <PICLIST@mitvma.mit.edu> wrote:

> I've made some minor modifications to the code, like set p=16f877,
> include "p16f877.inc", and add some debugging code to print the CRC
> out the serial port when entering CRC16.  In other words, nothing
> that should affect the CRC.
>
> When I run the code through the simulator (gpsim under Linux), I get
> correct results.  The CRC matches the ones in the comments as I step
> through the code.  However, when run on a real PIC (16F877 @ 4MHz),
> the results are wrong.  Note: the results in comments appear to be
> correct.  I've verified it with some C code on the desktop.  Here are
> the results from a real PIC from the serial port

    Dave:

    Twenty dollars says that the CRC is being calculated correctly,
    but your serial-out routine (and whatever other junk you've put
    between the PIC's registers and your eyes) is corrupting the
    data that you see.

    -Andy

    P.S.  In order to avoid using a temporary register, the author of
    your CRC code made it slow, large, and dangerously tricky.  If
    you don't mind using one extra register, you could improve the
    code quite a bit.

=== Andrew Warren -- aiw@cypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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