International Business Machines Corporation

Koji Kurachi

Kenji Ogasawara

Hiroshi Yanagisawa

Takao Matsui

Masaharu Kawamura

Hiroaki Suzuki

Hideo Asano

Kenji Kuroki

Kenji Okada

Takashi Nakamura

Akira Kibashi

Makoto Takase

Yuji Yokoe

Tatsuya Endo

Atsushi Tobari

Yuji Kigami

Tsutomu Numata

Hiromi Nishimiya

Katsumi Suda

Satoshi Hashimoto

Mayumi Okada

A method and apparatus for recovering from operation errors arising in an information recording and reproducing unit using a head with a GMR sensor is described. The read and write operations of the unit comprise executing a first error recovery procedure for recovering the operation error, executing a first GMR evaluation procedure for evaluating the performance of the GMR sensor when the operation error cannot be recovered by the first error recovery procedure, and applying a resetting pulse to the GMR sensor in accordance with the first GMR evaluation procedure.

Error recovery in unit using GMR sensor

A method and apparatus for accurately positioning the magnetic head of disk drives is disclosed. A recording medium is provided having two radial data structures formed thereon. Each radial data structure includes two parallel and adjacent data burst pattern trains. The first burst pattern is defined by a first side centrally aligned with a concentric data track and a second side opposed to the first side and centrally aligned with an adjacent concentric data track. The third burst pattern is defined by a third side spaced apart from the first side of the first burst pattern by a distance not greater than the read width of a magnetic head and a fourth side opposed to the third side and spaced apart from the second side by a distance not greater than the read width. The first radial data structure generates a first signal for positioning the magnetic head relative to the recording medium. The second radial data structure, parallel and offset from the first data structure, generates a second head position signal. Thus, the second head position signal is detected before the first head position signal becomes undetectable.

Magnetic recording medium magnetic head positioning method, and magnetic

A mechanism for compensating the servo data in a disk storage drive is provided. On each recording surface of a disk, a plurality of servo regions are diametrally formed in data regions along the diametral direction of the disk. In the servo region, a gray code (cyclic binary code) representing the address of a data track is recorded so as to correspond to the data track, and a burst pattern as a signal for positioning the head on the track are recorded. In the data track region, tracks are formed at a predetermined pitch P and in the tracks, a plurality of data is recorded. ID (Identification) is the identification information of the individual data. A servo compensation signal region is formed at a position sandwiched by the data region and the servo region known as the write recovery area. This is to compensate the servo signal in the servo region, thereby to enable error recovery when a read error or the like occurs in the servo region.

Recording medium having improved servo compensation and method for same

In a disk drive system, a circuit reduces the deterioration of the S/N ratio and corrects the position of a peak in a read signal to an accurate position. In one embodiment, a circuit senses the threshold levels corresponding to the magnitudes of three consecutive peaks of a read signal. A comparator obtains the direction of shift of the centrally positioned peak with respect to a reference position from the relationship of the magnitudes of the three consecutive peaks. The comparator outputs a pulse representing the direction of shift to a FIFO buffer. A delay circuit outputs a plurality of pulses. The pulses are shifted by an amount corresponding to a threshold level. A multiplexer selects a pulse to output from the delay circuit based on the direction of shift that was output from the FIFO buffer and based on the difference detected by an amplitude detection circuit. In an alternative embodiment, the correction circuit is implemented using a microprocessor.

Apparatus and method for correcting a read signal in a disk drive system

A disk drive having embedded servo information accesses data without using sector identifier recorded in each sector. When a signal sector pulse signal (SP) at the end of a servo area is detected in a dead state during start up, a first data state for the start of a sector transits to a second data state for the litter region of the sector being divided in accordance with the capacity stored in a current sector's pointer register. At the beginning of the sector, the contents of a next sector's pointer register is stored in current sector's pointer register and the contents of a next sector's operation register is stored in a current sector's operation register. Upon completion of sector processing, the first data state is maintained when the next sector is contiguous. When a terminate instruction is stored in current sector's operation register, the process moves to dead state. When the servo area arrives, the process moves to idle state. Responsive to this state, the magnetic head is activated to enable read and write operation for sectors having no sector identifier on the disk.

Information recording disk and drive system using no sector ID to

A magnetic head device comprising a magnetic core member made from a magnetic material having a positive magnetostriction constant and having confronting pole pieces separated by a non-magnetic material to form a transducing gap. A coil is wound around the magnetic core member so that a read signal can be read out from the coil, and a d.c. bias magnetic field is generated in the magnetic core member when a read signal is read out from the coil so that distortion of the read signal is suppressed.

Magnetostrictive head with d.c. bias magnetic field

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Yokohama, Japan

Koji Kurachi