Pseudo-random number generator based on a video control counter

摘要

An assembly of serially coupled XOR gates and an assembly of serially coupled shift register-XOR gate pairs are provided to a digital video system. The two assemblies are serially coupled to each other. The assembly of XOR gates generates a shift-in bit for the assembly of shift register-XOR gate pairs based on a cooperatively selected bit of a video control counter and a number of cooperatively selected feedback bits from the XOR gates of the assembly of shift register-XOR gate pairs it received as inputs. The assembly of shift register-XOR gate pairs in turn generates a pseudo-random number based on the shift-in bit and additional cooperatively selected bits of the video control counter. The XOR gate outputs of the assembly of shift register-XOR gate pairs are cooperatively mapped to the various bits of generated pseudo-random number. The pseudo-random number sequence is repeated when the video control counter is reinitialized to a predetermined value and the shift registers are cleared to a predefined state. The sequence length is sufficiently long to outlast a run of the video control counter before it is reinitialized for a new instance of the specified area controlled by the video control counter.