CIRCUIT DETECTING ABNORMALITIES OF OSCILLATION FREQUENCY FROM OSCILLATING MEANS

摘要

PROBLEM TO BE SOLVED: To provide a circuit which detects the abnormalities of an oscillation frequency without having to go through a software. SOLUTION: This abnormality detection circuit is provided with a detection circuit for detecting an abnormality of an oscillation frequency from an oscillating means; an initialization circuit 39 carrying out an initialization of the detection circuit 38 and a stopping of an action, a dividing circuit 40 for dividing an oscillation signal produced by a standard oscillating means comparing with the above oscillation frequency signal, a count circuit 41 for counting the pulse number outputted from the oscillating means outputted in a standard count period produced thereby, a retaining circuit 42, and a decision circuit 43 for deciding the normality or abnormality by a number value retained by the retaining circuit 42. An erroneous detection caused by a difference of the oscillation frequency due to an individual difference of the oscillating means which detects the abnormality by giving some range to a counter value for deciding normality by the decision circuit 43.