| 摘要 |
A method and apparatus for determining a relationship between an input signal frequency and a reference signal frequency is envisioned. The system derives a plurality of internal reference signals from the reference signal. The internal reference signals are provided to a level detection circuit which in turn samples the input signal a number of times within a period of time. Values associated with these samples are stored, as is one value of a sample from a previous period. The stored samples are correlated, and a relationship between the input signal frequency and the reference signal frequency is derived.
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