FW: [ethmac] CRC question

["Illan Glasner" <iglasner@zumanetworks.com>]

Hi,

       From some reason my replay Email didn;t appear till now so I will re-send it in hope this time it will pass the barrier.

have a nice day

   Illan

-----Original Message-----
From: Illan Glasner 
Sent: Friday, May 03, 2002 9:59 AM
To: 'ethmac@opencores.org'
Subject: RE: [ethmac] CRC question



Hi,

      Hope the following files will help you and any other who might be struggling with this crc as well as anyone who use crc RTL code in his behavoral instead of using task.

crc4.v :
basicly the first run you simple compile it and it calculate crc for few data.

than I took this data which have the crc value and push it back and got the magic number.

for the second run you need to use th +define+second_run

of course the second run 8 extra data are determine from the first run so it is not "general" solution but it should help yu see why you don;t get the right value in your crc

crc_calc_task.v
to make your simulation more effective I also added a task that you should use in any behavioral test bench which will calcualte the crc in zero time.

if you are intrested in how the crc equation are constract this task is the starting point as it have the basic single bit formula and than you can expand it for using it for any width as well as using De-Morgan rules you can get the equation for any width. (or simple go to asics site and get it done more quickly).

have a nice day

   Illan



-----Original Message-----
From: Christian R. Brecht [mailto:Brecht@cbedv.com]
Sent: Friday, May 03, 2002 3:42 AM
To: ethmac@opencores.org
Subject: [ethmac] CRC question



Dear All!

I know this is not an ethmac question but for you this will be an easy one:
I am working on my diploma work right now and for some reasons I cannot use
your ethernetcore as we need some special things implemented. But one thing
is similar: the CRC in general.
I guess I understood the CRC itself but for me it seems the CRC-32 for
ethernet needs some weird extras like inverting the 32 bits and reflecting
them as well. I will have to initialize the register with "F"s as the first
step.

Q: After all, usually I have to put zeros into the CRCC. Do I have to put 0s
into this CRC-32C as well, or do I need to put Fs to get it run (I need
nibbles for input). The problem is I have two "testpatterns", one does the
job (60 Bytes of zeros work with mine) the other doesn't. I used the CRC-32
from easics.com (CRC-Tool). I tried almost every combination. Am I doing a
major mistake?
Does someone of you have an 4:32-implementation of an CRCC (well, I am
programming in VHDL actually, but this should not be a problem)? Or another
testpacket? I would be really happy about that.

Thank you very much for your time reading this.



Sincerely yours,
Christian
university of applied technology cologne


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crc4.v

crc_calc_task.v