Abstract: A feedback and shift unit is arranged to reduce to a minimum the number of processing steps required in a processor, such as a DSP, to achieve a particular operating function, such as a linear feedback shift or a stepping function used by encryption algorithms. The feedback and shift unit (50) comprises a linear feedback shift register (52) for storing a value of the feedback and shift unit. A tap register (56) stores a tap position indicator indicative of tap positions for the feedback and shift unit (50). An input provides data to the feedback and shift unit. A feedback matrix, coupled to receive the data from the input, provides data bits, generated in response to the data and the tap position indicator, that are shifted into the linear feedback shift register (52) to form the value stored therein.

Abstract: A cyclic redundancy coder (10) is arranged to reduce to a minimum the number of processing steps required in a processor, such as a DSP, to achieve a cyclic redundancy coding function. The cyclic redundancy coder (10) comprises a shift register (12) having a plurality of storage elements each for storing a bit of a cyclic redundancy code word. A tap register (16) stores a tap position indicator indicative of tap positions in the cyclic redundancy code word that are subject to a logical operation. An input (18) provides input data to the cyclic redundancy coder. A logic feedback network (20-28) receives the data from the input and provides the logical operation. The logic feedback network also provides a plurality of data bits generated in response to the input data and each bit contained in each storage element identified by the tap position indicator. The cyclic redundancy code word is produced by applying at least one of the plurality of data bits to one storage element that is adjacent a tap position.