DIAGNOSTIC SYSTEM FOR COUNTER CIRCUIT

摘要

PURPOSE:To check whether or not a counter circuit is normally in operation and to prevent erroneous measurement by replacing an external input pulse signal with an internal pulse signal periodically and measuring the count. CONSTITUTION:The diagnostic system of the counter circuit is provided with an oscillation circuit 5 generating a pulse signal having an existing frequency and a selector circuit 3 to select the pulse signal or a measured pulse signal. The system provided with the oscillation circuit 5 and the selector circuit 3 in this way measures the number of pulse signals from the oscillation circuit 5 periodically for a prescribed time to calculate the frequency repeatedly. The adequacy of the counter circuit 2 itself is judged by comparing the calculated frequency with the substantial oscillation frequency of the oscillation circuit 5. That is, it is judged that the counter circuit is normal when the result of comparison is coincident and that the counter circuit is not normal when noncoincident.