Modifying check codes in data packet transmission

摘要

Disclosed is a method and circuit for modifying the check code of a data packet based on a first seed to accommodate the addition or substraction of a header. A number of bits, which include a second seed, an exclusive OR function of the first seed and a portion of a header, and a string of zeros dependent upon the length of an incoming data packet, is sent through a CRC generator. The resulting CRC calculation and the incoming packet check code are exclusive ORed to produce a modified check code taking into account the addition or substraction of the header.