Re: CRC Polynomial


"Rich Seifert" <usenet@xxxxxxxxxxxxxxxxxxxxxxx> ha scritto nel messaggio
news:usenet-245A85.08102810012006@xxxxxxxxxxxxxxxxxxxxxxx
> In article <7UIwf.23370$av6.12157@xxxxxxxxxxxxxxxxxxxxx>,
> "Lucyfero" <lucyfero@xxxxxxxxx> wrote:
>
>> <allanherriman@xxxxxxxxxxx> ha scritto nel messaggio
>> news:1136809615.348895.158630@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>> > kedarpapte@xxxxxxxxx wrote:
>> >> Is there any specific polynomial used for Ethernet PHY for Gb and 10Gb
>> >> range ethernet.
>> >
>> > The same 32 bit poly is used for all Ethernet rates.
>> >
>>
>> Yes is always the same:
>>
>> x(32)+x(26)+x(23)+x(22)+x(16)+x(12)+x(11)+x(10)+x(8)+x(7)+x(5)+x(4)+x(2)+x+1
>>
>> Only take care that it is transmitted MSB first (while all the other
>> fields
>> are LSB): does anyone know why ?
>>
>
> A common CRC implementation (especially in 10 Mb/s systems) uses a
> 32-bit shift register with feedback elements for the various terms in
> the polynomial above. The output of the shift register becomes the
> serial bit sequence transmitted onto the LAN. Sending the CRC from MSB
> to LSB means that, once the actual data is complete, the implementation
> can simply keeps shifting bits out onto the LAN for another 32 bit
> times; i.e., the hardware implementation is easier if the CRC is sent in
> the specified bit order.
>
>
> --
> Rich Seifert Networks and Communications Consulting
> 21885 Bear Creek Way
> (408) 395-5700 Los Gatos, CA 95033
> (408) 228-0803 FAX
>
> Send replies to: usenet at richseifert dot com

Thanks a lot Mr. Seifert ! We definitely need a new version of your great
book.

Thanks again

Luc


.

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