Magnetic disk drive

A magnetic disk drive comprising an active filter supplied with a read waveform of a magnetic disk, an A/D conversion means supplied with an output of said active filter, and a waveform equalizing means supplied with an output of said A/D conversion means, wherein said magnetic disk drive further comprises:

• an adaptive learning means for adaptively learning a boost characteristic of said active filter on the basis of an input and an output of said waveform equalizing means so that error in said waveform equalizing means is minimized;
• an abnormal learning detection means for detecting an abnormal operation in adaptive learning of said boost characteristic just after learning of a sector;
• and
• a boost characteristic resetting means for resetting the boost characteristic before adaptive learning to an initial value before adaptive learning of a next sector when abnormality occurs in adaptive learning of said adaptive learning means.

A magnetic disk drive comprising a digital waveform processing means capable of continuously reproducing a plurality of sectors of a magnetic disk, wherein said magnetic disk drive further comprises:

• a sampled data holding means for holding a row of digital sampled data corresponding to at least one sector in a front stage of a waveform equalizing means contained in said digital waveform processing means;
• and
• an abnormal sector detection means for detecting abnormality in an output signal of said digital waveform processing means whenever a sector is read;
• and wherein
• when said abnormal sector detection means detects abnormality in an output signal of said digital waveform processing means, said sampled data holding means holds a row of digital sampled data having said detected abnormality so that an abnormal sector is enabled to be decoded again by use of said data row held by said sampled data holding means.

A signal processing chip used in a magnetic disk drive for controlling read/write data of a magnetic disk, comprising:

• a waveform equalizing means for equalizing a read waveform;
• an adaptive learning means for adaptively learning an equalizing characteristic of said waveform equalizing means;
• a quality judgment means for judging quality of an output signal of said waveform equalizing means;
• and a function of discarding a result of learning obtained by said adaptive learning means in accordance with a result of judgment obtained by said quality judgment means.