| 摘要 |
PURPOSE:To prevent the malfunctions due to noise and to reduce the capacity of a back-up battery by setting a C-MOS gate between a power failure detecting circuit and a 1-chip CPU and supplying the level of said gate output signal to a reset signal generating circuit. CONSTITUTION:The drive voltage VCC outputted from a power supply circuit 11 is supplied to a 1-chip CPU13 as well as to a power failure detecting circuit 15. While the output voltage VM of a rectifier circuit connected between the secondary side terminals of a power supply transformer in the circuit 11 is supplied to the circuit 15. The circuit 15 outputs the power failure signal of an H level to a C-MOS gate 17 when the received voltage VM is reduced less than the prescribed voltage V0. Then the gate 17 converts the received power failure signal into another power failure signal PE of an L level to supply it to a service interruption detecting terminal of the CPU13 as well as to a reset signal generating circuit 16. The circuit 16 supplies the reset signal R of an H level to the reset terminal of the CPU13 in response to a state where the signal PF of an L level outputted from the gate 17 rises up to an H level. |
