Abstract: It is the object of the present invention to provide an improved peripheral unit, incorporating an MPU, that can reduce power consumption appropriately in accordance with mode transition when a host command from a host computer system is being processed, and a control method therefor. An MPU that requires a large amount of power, for example, is activated only when necessary, such as for the processing of a command (host command) from a computer system (host), and is deactivated during all other periods, by relinquishing the right of controlling of the operations to the respective sequencer circuits. The first sequencer circuit is activated only when necessary, such as for the transfer of data to the computer system. For the hardware operation of a device (e.g., writing data to or reading data from the device), the first sequencer circuit is deactivated, relinquishing the control right of that operation to the second sequencer circuit.

Abstract: A motor having enhanced transient characteristics during the acceleration time of the motor in a disk unit. The motor includes a motor controller having a phase-locked loop (PLL) or frequency-locked loop (FLL) for controlling the speed of a spindle motor in a disk drive. The PLL or FLL is coupled to a digital filter. The difference between a phase or frequency synchronized with the rotational speed of the motor and a target value is received by the digital filter. The digital filter output is added to the target value. The sum of the filter output and the target value is set in the PLL or FLL as an adjusted target value to perform PLL control or FLL control. With this arrangement, the time to shift from a low-speed rotation state to a high-speed rotation state can be shortened.

Abstract: The present invention provides a method and apparatus to efficiently switch heads in a disk drive. A disk drive comprises a plurality of recording surfaces and a plurality of heads and each head is opposed to a recording surface. The heads are used for reading data from or writing data to the plurality of recording surfaces. An offset quantity table stores an offset quantity for each of the plurality of heads. The offset quantity is a value representative of the distance of a head with respect to a reference head. A head sequence table stores a predetermined head switching sequence. Head switching operations use the head switching sequence stored in the head sequence table.

Abstract: The present invention provides a system, method and data format wherein a redundant sync byte or group of sync bytes is provided in a data sector at a distance sufficient to isolate the redundant sync byte from the primary sync byte in the event of multiple byte defects. In a first embodiment, a redundant sync byte, or group of sync bytes, is provided in the AGC field preceding the primary sync region. Upon failure to detect the primary sync byte, an attempt is made on a subsequent revolution to read the secondary sync byte, either by holding the AGC gain prior to reaching the data block, or initiating an "early read" just prior to reaching the data block. In a second embodiment of the invention, the redundant sync byte is provided within the data field subsequent to the primary sync region. On failing to detect the primary sync byte, the secondary sync byte can be read immediately or can be postponed until a subsequent revolution. The missed first data region is reconstructed using ECC information.

Abstract: A method and apparatus for damping actuator flex cable vibrations in a disk drive during actuator seek operations to improve disk drive performance. The actuator flex cable loop includes a damping element inserted in the J-block area of the actuator arm. The damping element can be foam, rubber, encapsulated visco-elastic material, spring clip supports or extensions of the cable support brackets. The damping element damps the vibrations of the dynamic loop of the actuator flex cable between the actuator assembly and the arm electronic bracket fixed to the disk drive housing. Decreasing the amplitude of vibrations coupled to the actuator assembly results in improved arrival performance of the disk drive during seek operations.