Abstract: The cut-off frequency and boost value of an analog filter on a read channel is set to initial values When the data is read from a disk, the read data is subjected to PR equalization at an FIR filter. At that time, a learning function provided on the FIR filter adjusts the tap coefficient so that an equalization error may be minimized. The cut-off frequency and boost value of the analog filter are modified until the adjusted tap coefficient has gone in a permitted range. After the tap coefficient of the FIR filter has gone in the permitted range, the cut-off frequency and boost value are stored in an EEPROM so that they can be used in a normal mode.

Abstract: A magnetic disk drive comprises a magnetic recording medium, a magnetic recording head for reading/writing data from/onto the magnetic recording medium, and detecting means for detecting thermal asperity by comparing the data read out from the magnetic recording medium with a predetermined value.

Abstract: A data reproducing apparatus for use in a hard disk drive (HDD) reproduces user data and servo data recorded on a disk. The apparatus comprises an A/D converter, a read PLL circuit, and a servo PLL circuit. The A/D converter converts signals read by a read head from the disk, to user data and servo data, both being digital data. The read PLL circuit generates sampling pulses, which are supplied to the D/A converter to reproduce the user data. The servo PLL circuit generates sampling pulses, which are supplied to the D/A converter to reproduce servo data. In the servo areas provided on the disk, the servo data is recorded, together with preamble patterns which the servo PLL circuit uses to perform phase acquisition.

Abstract: In a magnetic disk drive system in which a transducer addresses a plurality of tracks on a rotating magnetic disk, a programmable sector pulse generator responds to rotation of the magnetic disk and to an indication of the location of a track to be addressed by the transducer to generate sector pulses identifying a succession of sectors along the track. The indication of location of the track is provided by a central processing unit which divides the tracks into a plurality of concentric zones and then programs the sector pulse generator to execute different counts of timing pulses derived from the rotating magnetic disk in accordance with the particular zone in which the selected track is located. The central processing unit determines the zone of the selected track by counting track crossings of the transducer relative to a reference track, thereby eliminating the need to record zone identifying information in the tracks.