| 摘要 |
PURPOSE:To obtain the correct current time even in the case of a power failure by counting the frequency of the commercial power source and generating reference time when the commercial power source is connected, and counting reference pulses from an internal oscillator and generating reference time unless the commercial power source is connected. CONSTITUTION:Pulse counter means 7 - 9 count output pulses of the internal oscillator 2 and their counted values are reset when the rising of the waveform- shaped commercial power source 1 is detected by a rise detecting means 4 or when a specific counted value is reached. A state detecting means 6 detects the state of the commercial power source 1 according to a counted value at the time of the resetting to generate the reference time by a counting means 5 for clocking with a signal corresponding to the resetting of the pulse counter means 7 - 9 when the commercial power source 1 is connected or with the output pulses of the internal oscillator 2 unless the commercial power source 1 is connected. |
