US Patent 7590916 Cyclic redundancy checking value calculator

A CRC value calculator enables throughput to be improved while keeping down the increase in the size of the circuitry. This is achieved by using (n+1) basic CRC circuits to configure a CRC value calculator in which the width of the data processed during one clock cycle is m2n bits. For example, when m2n bits is the data width processed per calculator cycle, the CRC value calculator of this invention is configured by using selectors to serially connect a CRC circuit that processes every m2n bits, a CRC circuit that processes every m2(n−1) bits, . . . , and a CRC circuit that processes every m20 bits. This configuration makes it possible to calculate a correct CRC value even when the remainder of an input network frame is not a multiple of m2n bits. Selectors are used to select CRC circuit output according to process data width. Reduction of the operating frequency is avoided by using registers to form a pipeline between CRC circuits.