| 摘要 |
The objective of the invention is to provide technology to give high-speed DVD RF signal reading. Frequency comparison circuit 1 of the present invention has edge spacing detection circuit 3, maximum spacing detection circuit 4, and minimum spacing detection circuit 5. The number of reference clock pulses in response to an RF signal pulse width (edge spacing) is detected by edge spacing detection circuit 3. The maximum value of the edge spacing in one frame, that is, the maximum edge spacing, is detected by maximum spacing detection circuit 4. The minimum value of the maximum edge spacing in multiple frames is detected by minimum spacing detection circuit 5. The maximum edge spacing minimum value is compared with a number that indicates the frame synchronizing signal period to perform frequency comparison. Edge spacing detection circuit 3, maximum spacing detection circuit 4, and minimum spacing detection circuit 5 are each constituted with registers. Frequency comparison is thus possible without using slow-speed comparators or counters, so that the operating speed can be increased compared with circuits of the prior art that use such comparators and counters.
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