Re: [usb] crc algorithm

["RE Tambunan" <kebloo@mitra.net.id>]

On 20 Feb 2002 at 11:32, Bo wrote:

> Does anybody know what value we should
> prefill for this CRC calculating?
> For example, ATM 32-bit CRC should prefill
> all 1's, but some HDLC, Ethernet stuff need
> to prefill all 0's.
> What's the reason for doing that?
> Is it true Single String Feed Back need to 
> prefill 0's?
For USB, register value is filled with 1s before CRC calculation.
It is stated in USB 1.1 & USB 2.0 specification section 8.3.5
at 2nd paragraph. The reason is to protect also leading 0s
in front of a packet. This is the reason stated in the " CRC
in USB" whitepaper.

What I don't know is about the binary bit representation of
Generator Polynomial. Could you help me with that
information? Or another on-line reference maybe?

> 
> regards
> bo
> 
Best Regard,


RE Tambunan
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