Finnegan, Henderson, Farabow, Garrett, and Dunner
Apparatus for generating index signals, for use in magnetic recording/reproducing apparatuses
 This invention relates to an index signal generator of magnetic disk drive. The peak of a magnetic field from a magnet rotating in association with the rotation of the spindle in detected by a peak detecting circuit. A detection pulse signal output circuit outputs a detection pulse signal synchronously with the peak of the magnetic field on the basis of the result of the detection of the peak detecting circuit. A memory for storing adjustment data is provided. This adjustment data corresponds to the time after the detection pulse signal was output until the index pulse signal is output. An index pulse signal output circuit outputs the index pulse signal on the basis of the adjustment data stored in the memory after an expiration of the period of tiem corresponding to the adjustment data from the output of the detection pulse signal. 
Kabushiki Kaisha Toshiba
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Masaki
Sano