Nios - Ethernet Frame Format

Hi, 

I would like to know if the Ethernet packets sent through the Nios
Ethernet Kit, do they have a 32-bit CRC as the trailer.

If there is a CRC trailer does the Nios software and hardware check
this automatically?  And if there isn't a 32-bit CRC trailer, how can
we calculate and add this?

Thanx

Colin wrote:
> And if there isn't a 32-bit CRC trailer, how can
> we calculate and add this?

You can do it in SW (using NIOS) or FPGA. Latter one is of course much 
faster but takes some resources.

Try googling for "crc32 calculation". I've used this source for SW 
implementation: 
http://cell-relay.indiana.edu/cell-relay/publications/software/CRC/32bitCRC.c.html

And if you want to do it in HW, try this tool that generates 
synthesizable VHDL/Verilog:
http://www.easics.com/webtools/crctool

-JS-

csim036@ec.auckland.ac.nz (Colin) wrote in message news:<eeab73c0.0407072122.3ceee0e@posting.google.com>...
> Hi, 
> 
> I would like to know if the Ethernet packets sent through the Nios
> Ethernet Kit, do they have a 32-bit CRC as the trailer.
> 
> If there is a CRC trailer does the Nios software and hardware check
> this automatically?  And if there isn't a 32-bit CRC trailer, how can
> we calculate and add this?
> 
> Thanx


Hi,

In addition to the other reply on your question: end of frame CRC
(sometimes called FCS) can be calculated in hardware on many Ethernet
MACs; this way it is done independently of the CPU. I'm not sure if
all MACs do this, but when I was messing with the opencores.org
Ethernet MAC it had this capability... the software that talks to the
MAC had to enable CRC generation on a frame-by-frame basis -- so given
this I would highly recommend getting the data sheet of the Ethernet
MAC you're using to see if it supports this feature.

Jesse Kempa
Altera Corp.
jkempa at altera dot com

Thanx guys I really appreciate you help.