METHOD AND APPARATUS FOR COMPUTING @$apos;N-BIT AT A TIME@$apos; CRC@$apos;s OF DATA FRAMES OF LENGTHS NOT MULTIPLE OF N

摘要

Abstract of the Disclosure;The present invention discloses CRC checking 'N-bit at a time' of data frames of lengthsnot necessarily in a multiple of the N-bit. While receiving the data frame, the data framelength is extracted from the protocol header and a misalignment is computed versus the'N-bit at a time' value. Simultaneously, CRC is computed on each received N-bit of thedata frame and an FCS register is updated. At each cycle, a checking is performed toknow whether the data frame length has been extracted from the protocol header. Whilethe data frame length is not yet known and more bits are left to process, the data frame iscontinued to be received and computed 'N-bit at a time'. When the data frame length isknown and no more bits are to be processed, the current value of the FCS register iscompared to a pre-stored vector corresponding to the misalignment. If a match occurs,checking of the data frame passes and the data frame is accepted. If a match does notoccur, checking of the data frame fails and the data frame may be rejected. Therefore, thepresent invention is capable of computing CRC of a data frame 'N-bit at a time' while thedata frame length is not yet known.