[ethmac] Re: crc magic number

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

3-May-01

   Hi,

	I just got another Email as for the magic number and since this
is the second I got with almost the same question I enclosed my answer
so if anyone else have similar question they can see the answer.

in both Email I got the CRC Equations and a question of how come the
magic number "refuse" to appear.

so here a copy paste of my first answer :

----------------------

Your equation are ok tho' not in the regular fashion order as the data
is in nibble order but the nibble are bit swap.

Enclosed a file you can run to get your magic number with your equation
I simple save them and add small test bench.

basicly you first run the crc4.v and you get the crc you need to append
than you run it with +define+second_run and it will than also run the
append crc and you will see the crc magic.

you can still send the number the way you did BUT in this case once you
get what you think is the right crc you need to do bit swap on nibble
boundry. or you need to make the rotation like you can see in the test
bench I enclosed in any case this bit shaffling take no logic so no need
to be concern, just do as you like.

I enclosed also the second run verilog.log file so you can see.

have a nice day

   Illan

----------------------

have a nice day

   Illan

crc4.v

verilog.log