| 摘要 |
PROBLEM TO BE SOLVED: To provide a detecting circuit which performs based on a clock with followability to revolving fluctuation of a spindle motor and stability independent of a reading area so as to accurately detect a synchronizing pattern located at the beginning of a data area and a re-synchronorizing pattern laid in the data area and can recover effectively synchronization by the re-synchronizing pattern if the synchronizing pattern is failed to be detected. SOLUTION: A controlling means 1, a counter 2, and a re-synchronizing pattern detecting window generating means move in sync with a clock 2 made from lead data. A clock 1 is obtained by multi-plying a fixed clock obtained from a crystal oscillator with a PLL. The counter 2 setting a length of one data block as an initial value starts subtracting operation when a synchronous pattern detecting window synchronized with the clock 1 is input in a circuit. When a pattern is detected within the synchronous pattern detecting window or a re-synchronouizing pattern detecting window, a counter value is reset to a value set in advance. A window is generated from the counter value.
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