| 摘要 |
A magnetic disk drive capable of specifying even the type of a medium defect with a small number of read/write operations is disclosed. A read signal is sampled. A defect detector 40 of a read channel IC includes a (1+D) calculation circuit 41 for adding the current and preceding sample values or the absolute values thereof. The two types of sums of the current and preceding samples are compared with a lower reference value and an upper reference value preset in comparators 42, 43, respectively. A portion where the sum of the sample values exceeds the upper reference value is detected as a medium defect due to thermal asperity, a portion where the sum of the absolute values of the sample values is lower than the lower reference value is detected as a medium defect due to a missing, signal and a portion where the sum of the absolute values of the sample values exceeds the upper reference value as a medium effect due to an extra, signal thereby generating a defect detection signal DD. Three types of defects can thus be detected with a single read operation.
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