| 摘要 |
PURPOSE:To prevent writing data from jittering even when a defect is present at the part except the synchronizing pattern part of a servo disk surface by sending a gate signal to close the output gate of a pattern detecting circuit when the comparing result of the phase of a basic synchronizing clock pulse and a synchronizing pattern is asynchronous. CONSTITUTION:For a signal S1 read by a servo head 1, a synchronizing pattern S2 only is sampled by a pattern detecting circuit 2, and a clock generating circuit 3 execute the loop control so as to compare in phase a basic synchronizing clock pulse being self-oscillated and the synchronizing pattern S2 and synchronize them. A synchronizing pattern detecting circuit 5 generates a gate signal S5 for a synchronizing pattern with the signal S2 and a signal S3. When the synchronous/asynchronous signal S4 transfers asynchronization, the output gate of the pattern detecting circuit 2 is closed. Thus, while a defective part is present, a new pulse is not outputted to the signal S2, and a basic synchronizing clock pulse S3 does not receive the bad influence due to the defect of a disk surface.
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