| 摘要 |
<p>PURPOSE:To obviate the generation of the advance or delay of the period watch and to enable the execution of a clocking operation by using AC signals by discriminating the difference in the frequency of the AC signals from a commercial AC power source. CONSTITUTION:A microprocessor 1 is operated by the reference signal supplied from a signal transmitter 3. The reference signal from the transmitter 3 is frequency-divided to the reference clock of a prescribed period by a frequency divider 5 and is counted by a counter 9. The signal subjected to waveform shaping in an AC waveform shaping device 7 is supplied as an interrupting signal via an interruption controller 11 to the processor 1 by which the interruption is caused in the processor 1. The period of the measured AC signals is compared with the prescribed threshold value and the nominal frequency of the AC signals is decided. The AC signals of the commercial AC power source are counted and the clocking operation is executed every time when the count value of the AC signals attain the prescribed count value corresponding to the decided normal frequency.</p> |
