[usb] Clarification in USB

[Ravi Kumar <ravikumar_vlsi@yahoo.co.in>]

hi,
Vikas Would u pls tell me how did they arrive at a
value 800d as a residual polynomail
In General reciver checks for zero value in crc after 
manipulating the crc for entire received data.

Pls Reply ASAP
With Regards
Ravikumar

 --- Vikas T Rao  <vikasraot@myw.ltindia.com> wrote: >
** Proprietary **
> 
> hi,
> 
> i hope u might be very new to the USB protocol. the
> problem can be better understood if u read the USB
> Spec. however i am giving a brief explanation of it
> below.
> 
> CRC is used for checking whether there is any error
> in the data received. if u can go into 8.3.5.2 of
> USB Spec1.1, the residual polynomial for the error
> free data reception should be equal to 800Dh. hence
> in the assignment, that value is used to check
> whether all the received bits(data & CRC fields) are
> correct or not.
> 
> ...vikas.
> 
> >>> koyo@itri.org.tw 09/25/02 02:16PM >>>
> Hello!! Everybody
> 
> I have the question about the opencore USB core.
> The original verilog code is following :
> assign crc16_err = data_done & (crc16_sum !=
> 16'h800d);
> I don't understand why the check number of CRC16 is
> 800d(Hex).
> 
> best regards  
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