| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology which speeds up a read of the RF signal of a DVD. SOLUTION: This invented frequency comparator circuit 1 has an edge interval detecting circuit 3, a maximum interval detecting circuit 4, and a minimum interval detecting circuit 5. The edge interval detecting circuit 3 detects the number of pulses of a reference clock corresponding to the pulse width (edge interval) of the RF signal, the maximum interval detecting circuit 4 detects the maximum value of edge intervals in one frame, i.e., the maximum edge interval, and the minimum interval detecting circuit 5 detects the minimum value of maximum edge intervals of plural frames; and the minimum value of the maximum edge interval is compared with a number representing the period of a frame synchronizing signal to make a frequency comparison. The edge interval detecting circuit 3, maximum interval detecting circuit 4, and minimum interval detecting circuit 5 are all composed of registers and the frequency comparison can be made without using a comparator nor a counter which are slow in operation speed, thereby the operation speed can be increased as compared with a conventional circuit which uses a comparator and a counter.
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