Consumer Electronics

PACKET FORMAT

As indicated in Fig. 42.9, a packet contains three major fields : the header, the message, and the redundancy check bits. Generally speaking, the control information associated with a particular message or link is included in the header of a message packet. Some packets may not contain a message field if they are being used strictly for control purposes. Although a variety of techniques for generating redundancy checks are possible, the most popular technique uses cyclic redundancy checks (CRCs). Basically, a CRC is nothing more than a set of parity bits that cover overlapping fields of message bits. The fields overlap in such a way that small number of errors are always detected and the probability of not detecting the occurrence ...