| 摘要 |
PURPOSE:To decide the presence or absence of a clock to be inputted signal and the propriety of frequency by providing a receiver, a band pass filter, a comparator and a rectifier circuit. CONSTITUTION:A receiver 1 outputs a clock of the same frequency as the input clock frequency in receiving a clock signal 6 of a specified level or above and outputs a prescribed constant level when the level of the input signal is a specified value or below. When the clock signal 6 is within the specified frequency range, the output level of the band pass filter 3 is larger than the threshold level of the comparator 4 and a clock subjected to waveform shaping is outputted as the output of the comparator 4. The rectifier circuit 5 outputs an H level signal when the clock 14 is a prescribed level or below and has a duty ratio, and when not, the L level signal is outputted. Thus, an internal circuit 8 recognizes whether or not the normal clock is to be received. |
