RE: [ethmac] CRC Magic number! How to figure out c704dd7b?

["Kevin Kay" <Kevin.Kay@espipd.com>]

The magic number does come out correct.  You should run a test frame
through the MAC and the back into the receiver to check, but those of us
that have implemented portions of the design have had no problems
communicating with other systems (at least I haven't).

Regarding the source of the magic number, this is really a error-coding
theory question for cyclic codes.  The magic number is a function of the
polynomial used to generate the code.  There are several popular
reference texts out there.  I've found that most application notes brush
over the theory and offer practical implementations only (although I've
not read the Xilinx note).

Regards,
Kevin

-----Original Message-----
From: Jun Zhang [mailto:zhang_jun@tsinghua.org.cn]
Sent: Sunday, October 13, 2002 10:06 PM
To: ethmac@opencores.org
Subject: Re: [ethmac] CRC Magic number! How to figure out c704dd7b?


Hi:
         In my mind, Xillinx has such a application note about CRC.
         You may look for it in their web site. Also , you may find the
file
         crc_v3.txt at ftp: ftp://ftp.rocksoft.com/papers/.
         I think it's really a good reference .
         Anyway, I have another question .  FCS data was transmitted in
a
         order of D31,D30,D29 ....D1,D0. It's different from the
transmit 
order of
         other fields of MAC frame. If just calculating the whole
packet's 
CRC without
         changing the byte order of FCS field, can it get the result of 
c704dd7b?
         I really think it won't get the number. Anyone agree with me?

At 11:19 2002-10-11 -0100, you wrote:
>Dear All:
>I need the information or documentation about how to figure out the
>CRC magic number,c704dd7b.
>I've searched AMD Site that Allan said befor.
>However, I didn't get any documentation to reference.
>Could Allan or someone tell me that where I can get more information
>about CRC magic.
>I've searched Google, But still nothing at all.
>Therefore, I come here for helping.
>All I want to know is how to figure out it?
>Thanks!
>
>Have a nice day
>--
>To unsubscribe from ethmac mailing list please visit 
>http://www.opencores.org/mailinglists.shtml



---
Best regards.

Jun Zhang

Phone: 010-88354422-114
Mailto: zhangj99@mails.tsinghua.edu.cn



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