| 摘要 |
PURPOSE: To surely detect a fault that reset or set is not performed even when reset signals or set signals are inputted to respective flip-flops inside a counting circuit. CONSTITUTION: This counting circuit is provided with a fault detection part 4 and serially connected plural T flip-flops 1A, 2 and 3 and uses the T flip-flop with a set terminal and a reset terminal for the T flip-flop 1A of an initial stage. The fault detection part 4 inputs positive pulses to the set terminal and reset terminal of the T flip-flop 1A of the initial stage before counting is started and detects the degradation fault of the set terminal and the reset terminal. At the time, by changing the order of inputting the positive pulses to the set terminal and the reset terminal, which one of the set terminal and the reset terminal causes the degradation fault is discriminated. Also, by tentatively inputting the reset signals after the counting is started and restarting the counting, the degradation faults of the reset terminals of the T flip-flops 2 and 3 other than the initial stage are detected. |
