PROGRAMMABLE SYNDROME ARITHMETIC CIRCUIT

PURPOSE:To realize all syndrome arithmetic circuits with one set of the hardware by connecting plural D flip-flops in series via an arithmetic circuit controlled by an external 2-bit digital signal. CONSTITUTION:The arithmetic circuits 40-4n are operated in four ways depending on the value of control signals Xi, Yi. When Xi=0, Yi=0, the input from a pre-stage flip-flop (hereinafter FF) is outputted to a DFF of the next stage as it is. When Xi=0, Yi=1, the input from the pre-stage DFF is fed back as it is to each arithmetic circuit. When Xi=1, Yi=0, the exclusive OR between the input from the pre-stage DFF and the feedback input is outputted to the next stage DFF. When Xi=1, Yi=1, the exclusive OR between the feedback input signal and the input signal from the pre-stage DFF is fed back to each operating circuit. Thus, the syndrome arithmetic circuit corresponding to all polynominals is realized by giving a proper value to control lines Xi, Yi.