| 摘要 |
PURPOSE:To obtain a drift detecting circuit which can be used without adjustment by clearing a counter by one input pulse, starting to count a clock, stopping to count a counter by other input pulse and detecting by the drift of the voltage control oscillator whether or not the counted value of the counter exists in a certain prescribed value. CONSTITUTION:An input signal is divided to 1/N by a 1/N frequency dividing circuit 1, the waveform is also corrected, enters the PL terminal of a phase comparator 2, a flip-flop circuit 10 is set by the divided pulse signal and a counter 12 is cleared. On the other hand, the output pulse of the 1/M frequency dividing circuit 5 also enters a PM terminal of a phase comparator 2, the flip flop circuit 10 is set by the output pulse, and the pulse goes to a reading pulse of a flip flop 14. A detecting circuit 13 decides that the drift exists when the counted value shown by the counter 12 is smaller than the prescribed value C1 or larger than the prescribed value C2, and decides that the drift will not exist when the value is larger than the prescribed value C1 and smaller than the prescribed value C2. Thus, the drift detecting circuit, which can be used without adjustment, can be realized. |
