FSK DEMODULATION CIRCUIT

PURPOSE:To reduce remarkably a time occupying exclusively a microcomputer for demodulation by deciding the binary level of a digital signal according to the count of a counter and resetting the counter. CONSTITUTION:A counter counts a signal only when a pulse signal S4 is at high level and interruption for demodulation is applied to the microcomputer 25 in the timing of the falling edge by the pulse signal S4. Thus, the microcomputer 25 applies demodulation processing for a prescribed period from the falling edge timing of the pulse signal S4 and the exclusively occupied time of the microcomputer 25 for demodulation is reduced remarkably.