Pseudorandom number generating method and pseudorandom number generator

A pseudorandom number generator comprising a plurality of orderly pseudorandom number generating circuits, each said pseudorandom number generating circuit being adapted to generate a first pseudorandom number on a basis of a first pseudorandom number generated by a preceding said pseudorandom number generating circuit, a second pseudorandom number being generated from the first pseudorandom numbers generated by the plurality of said orderly pseudorandom number generating circuits, each said pseudorandom number generating circuit comprising:

• a register for taking in and holding a state data composed of a plurality of bits in synchronism with clock pulses of a clock signal;
• a first and second function generator circuits for producing a first and second data each composed of a plurality of bits correspondingly to the state data thus held in said register;
• a first selector for selecting and supplying a specific bit of either the first or second data according to the first pseudorandom number generated by said preceding pseudorandom number generating circuit as the first pseudorandom number of said pseudorandom number generating circuit;
• and
• a second selector for selecting one of the first and second data, except the specific bit thereof, according to the first pseudorandom number generated by said preceding pseudorandom number generating circuit and supplying the selected data to said register as the state data.