MAIKUROKONPYUUTA

摘要

PURPOSE:To prevent error from generating in the calculation of the average value by detecting the least operating voltage of an analog circuit and inhibiting the fetching of the output signal of the analog circuit having an error with use of the voltage detection signal. CONSTITUTION:An analog circuit has an abnormal operation when the power voltage drops and a CPU sometimes has a normal operation owing to a fact that the least operating voltage of the analog circuit has a level higher than that of the CPU. Under such conditions, the output signal of the analog circuit shows the wrong data and therefore the arithmetic result has an error. In this respect, a power voltage detecting circuit is provided and a digital signal processing circuit 3 stops temporarily the fetching of the processing result of an analog signal processing circuit 2 in accordance with the power voltage detection signal. Then the average value can be calculated with exclusion of the processing result of the circuit 2.