| 摘要 |
PURPOSE:To attain excellent reliability and stability with less number of components than a conventional circuit by using a presettable down-counter so as to apply both the count of a measured pulse and the comparison with a setting value. CONSTITUTION:The presettable down-counter 16 reads a preset value N from a setting device 20 in the trailing timing of a reset signal RE and applies down- count at each trailing of the pulse S2 to be measured shaped into a square wave by a waveform shaping circuit 18. When the pulse S2 to be measured is inputted, a borrow signal B is outputted from the counter 16 within the period T. An output Q of a flip-flop 22 is read by a latch circuit 24 of the next stage in the trailing timing of a latch signal RA and the output of the latch circuit 24 is a decision output OUT. Thus, the constitution is simplified in comparious with a circuit using a digital comparator so as to compare the count and the setting value and the title circuit is realized inexpensively.
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