Abstract: In order to bring and keep a slave phase of rotation of a slave spindle into and in synchronism with a master phase, the master phase is represented in a predetermined time duration by zeroth through (N-1)-th master region data with an N-th master region datum added, where N represents a predetermined integer which is not less than two. The slave phase is represented, during one rotation of the slave spindle, by zeroth through (N-1)-th slave region data with an N-th slave region datum additionally used to provide a guard time. The zeroth through the (N-1)-th slave and master region data are compared to render a phase difference between the master and the slave phases either to zero or to a predetermined value. Alternatively, the master phase is represented in the predetermined time duration by a sequence of composite pulses which comprise N master clock pulses with at least one of the clock pulses omitted to indicate a start point of the sequence.

Abstract: In order to bring and keep a slave phase of rotation of a slave spindle into and in synchronism with a master phase, the master phase is represented in a predetermined time duration by zeroth through (N-1)-th master region data with an N-th master region datum added, where N represents a predetermined integer which is not less than two. The slave phase is represented, during one rotation of the slave spindle, by zeroth through (N-1)-th slave region data with an N-th slave region datum additionally used to provide a guard time. The zeroth through the (N-1)-th slave and master region data are compared to render a phase difference between the master and the slave phases either to zero or to a predetermined value. Alternatively, the master phase is represented in the predetermined time duration by a sequence of composite pulses which comprise N master clock pulses with at least one of the clock pulses omitted to indicate a start point of the sequence.

Abstract: In a disk drive where data bits containing a bit sequence signifying a specified location of a data block are read from a disk. A reference bit sequence identical to the recovered bit sequence is generated. Each of the recovered bit sequence and the reference bit sequence is divided into M groups of K bits. The M groups of the recovered bit sequence and the corresponding M groups of the reference bit sequence are compared with each other and a coincidence signal is produced for each of M pairs of compared groups when there is a bit-by-bit match therebetween. A match detector determines if the coincidence signal is generated from all pairs of the compared groups or from N out of M pairs of the compared groups.

Abstract: A hard-disk storage apparatus is provided with a plurality of stacked magnetic recording disks each of which is provided with a plurality of tracks. Each of the tracks is specified by a cylinder address and a physical data-head address. Logical data-head addresses applied to the hard-disk are converted into the corresponding physical data-head address according to a conversion table pre-recorded within a non-volatile memory. Further, offset parameters of each data-head over two selected cylinders at predetermined temperatures are previously stored within the non-volatile memory. A microprocessor unit calculates offset parameters of all the data-heads over each of the tracks at a given temperature preferably measured within the hard-disk storage assembly. These offset parameters are utilized to correct the displacement of each data-head over a given track due to temperatures.

Abstract: A magnetic disk drive includes a spindle for rotating a plurality of magnetic disks and a lock mechanism for preventing the spindle from rotating when the magnetic disk drive is not operated. A toothed disk is provided on an axial end of the spindle, and a movable lock arm engageable to teeth of the toothed disk is provided. The lock arm is driven to lock the rotation of the spindle by a solenoid which is energized after a predetermined period of time has elapsed after the electric power of the disk drive is turned off, so that the lock mechanism locks the spindle after the rotation of the spindle and magnetic disks completely stop.

Abstract: A magnetic disk apparatus for reading and writing user's data from a magnetic disk having a data surface with a plurality of concentric data tracks the data surface having a void area in which user's data is inhibited. The magnetic disk apparatus includes a magnetic head for reading and writing the user's data from and to the data tracks, detecting apparatus for detecting a circumferential position of the magnetic head at a target track, a store for storing the position and length of the void area, a timing clock generator for generating a read/write synchronization signal and control circuitry for preventing transmission of the read/write synchronization signal during a time period corresponding to the length of the void area when the circumferential position of the magnetic head corresponds to the position of the void area, thereby inhibiting read-out or write-in to or from an interface circuit while transmission of read/write synchronization signal is prevented.