systematic set of screening for a shift register.

摘要

A shift register which is formed by a memory, the number of shift stages of the shift register is determined by the count value of a counter and designating a read address of the memory by a value obtained by subtracting an arbitrary constant from the count value of the counter through an operator. A multiplexer is provided at the input side of the operator. Output data, obtained by selecting a constant for determining the number of shift stages of the counter and a scan address in accordance with a scan enable signal, are provided to the operator. When the constant for determining the number of shift stages of the counter is input, the operation of the shift register is carried out and when the scan address is input, the content of each stage of the shift register is scanned out.