Re: [usb] about crc

["Vikas T Rao " <vikasraot@myw.ltindia.com>]

** Proprietary **

hi,

token CRC is used for token packets only and data CRC for data packets only. no CRC is there for handshake packets.

G(X)=X5+X2+1 : X5 indicates that 5 bits are used for token packets. X2+1 indicates the polynomial to be used is "00101" for calculation of CRC. note that '1's in the polynomial are appearing at X2 and X0 location.

G(X) = X16+X15+X2+1 : X16 indicates that 16 bits are used for data packets. X15+X2+1 indicates the polynomial to be used is "1000000000000101" for calculation of CRC. note that '1's in the polynomial are appearing at X15, X2 and X0 location.

read the spec and try to understand how the CRC has to be calculated with these polynomials independently for token and data packets.

...vikas.


>>> workingmail@163.com 08/12/02 12:48PM >>>

    hello,everyone.I am a newbie to usb, and I am confused by the crc equation.TOKEN CRC :G(X)=X5 +X2 +1,DATA CRC:G(X) = X16 + X15 + X2 + 1. Can anyone tell me the meaning of them and the relation between the two equations and the implementations in the opencore's program.
	thanks a lot for your answer!  
  



              workingmail@163.com 
                 2002-08-12
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