[ethmac] RE: doubt!!

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

Hi,

   This question I was already been asked in the past and so incase other looking for the same info, if you are using any interface which is wider than your input data you need to preload your crc machine with value differ than the all 1's.

assumign you are working in boundary of byte than the value are :

8   (10011011111100011010100100001111)
16  (00001001101110010011100001011001)
24  (10000001011001000111010011000101)
32  (01000110101011110110010001001001)
40  (00110011100111111101111000101111)
48  (01101000101110010011001011110101)
56  (10010101010110100110000101100010)

the above mean if the data have 8 bit less than the full input use the first line if it have 16 bit less than use the seocnd line etc up to 56 bit.

BTW there is really no reason to developed crc machine it is a waste of time and lot of work using excell spread sheet. simple go to http://www.easics.be/webtools/crctool which put an excelent tool that will generate for you the crc equation and save time.

have a nice day

  Illan   


-----Original Message-----
From: Muthumari S - CTD, Chennai. [mailto:muthus@ctd.hcltech.com]
Sent: Thursday, January 10, 2002 7:18 AM
To: Illan Glasner
Subject: doubt!!



I developed a verilog module to calculate crc-32; 64bits (8bytes) at a time.
As long as i have the data width of 8 bytes i don't have any problem with my
module. I am going to use this module for 10gbps ethernet application. so,
if the data frame length is not multiple of 8bytes; how should i calculate
crc-32. ie., if my last 8bytes, not necessarily all the bytes are valid. 

say, for example if only 3 most significant bytes are valid in my last
8bytes of data. How could i modify the data so as to get the crc-32 value
valid only for that 3bytes in the last 8bytes.

For the past 1 week i have been browsing the internet to get answer for
this, But i couldn't get anything.

Can u give me an idea to get out of this problem?????


Thanks in advance.


Regards,

   S.Muthumari 
   MTS 
   HCL Technologies Ltd., 
   Chennai. 
   Mail ID :  muthus@ctd.hcltech.com 
   
   Ph:  6230711( 4-lines )   Extn : 2539 
"one who desires nothing for himself, is desired by all" 

Disclaimer: 
This document is intended for transmission to the named recipient only.  If
you are not that person, you should note that legal rights reside in this
document and you are not authorized to access, read, disclose, copy, use or
otherwise deal with it and any such actions are prohibited and may be
unlawful. The views expressed in this document are not necessarily those of
HCL Technologies Ltd. Notice is hereby given that no representation,
contract or other binding obligation shall be created by this e-mail, which
must be interpreted accordingly. Any representations, contractual rights or
obligations shall be separately communicated in writing and signed in the
original by a duly authorized officer of the relevant company.






--
To unsubscribe from ethmac mailing list please visit http://www.opencores.org/mailinglists.shtml