RE: [usb] crc algorithm

["kw@nie" <kwanie@pacific.net.sg>]

I think I know why the binary representations, in the USB specification, are
different from the polynomials. Attached is a brief explanation based on the
5-bit CRC but the principle applies for both CRC generators.

Cheers,
kwanie




 -----Original Message-----
From: 	owner-usb@opencores.org [mailto:owner-usb@opencores.org]  On Behalf
Of kebloo@mitra.net.id
Sent:	21 February 2002 08:34
To:	usb@opencores.org
Subject:	[usb] crc algorithm

Hello,

Sorry for this beginner question, but I wish some one could
answer my curiosity...

USB 1.1 specification defines generator polynomial of 5-bit crc
as G(x) = x^5+x^2+1 and binary pattern that represent it as
00101B and 16-bit crc as G(x) = x^16+x^15+x^2+1 and
binary pattern that represent it as 1000000000000101B.
My question is why the binary pattern stated like that and
not 100101B for 5-bit crc and 11000000000000101B ?
Thanks....



Best Regard,


RE Tambunan
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crc5.JPG