Abstract: The present invention is a method and apparatus for positioning a dual element magnetoresistive (MR) head relative to a storage medium in a storage device. The MR head has first and second MR elements. The storage medium is mounted in the storage device to allow relative movement between the MR head and the storage medium. The storage medium includes servo information provided to induce first and second thermal responses in the MR elements. A controller is coupled to the MR head and controls the relative movement between the MR head and the storage medium using the first and second thermal responses in the MR elements.

Abstract: A method of and a system for efficiently using split information stored in an unnecessary data sector, thereby reducing unnecessary data.

Abstract: When a reproduced signal is outputted from the MR head to the envelope detector, the positive envelope joining positive peaks and the negative envelope joining negative peaks are outputted from the envelope detector to the asymmetry detector. An asymmetry value or fluctuation value of the reproduced signal waveform can be found through comparison of the positive envelope and negative envelope and calculation at the asymmetry detector. If these values do not fall within a desired or permissible range, a high degree of asymmetry is indicated in the reproduced signal waveform, and the sense current controller accordingly alters the sense current value. This operation is continued until the envelope of the reproduced signal waveform resulting from the new sense current falls within the desired or permissible range.

Abstract: A system for halting operation of a hard disk controller when a write operation occurs during a servo positioning error condition including a memory cell for retaining an indication of whether a write operation occurred during the previous servo sector. A memory cell, such as a flip flop, is set on any occurrence of a write operation. With the reading of a next servo field, the output of the first flip flop is latched to a second flip flop. During a present servo sector, a servo positioning error signal is logically AND'ed with a write gate active signal where the write gate active signal is enabled if write gate is active in the present servo sector or write gate was active in the previous servo sector (as indicated by the output from the second flip flop.

Abstract: A servo pattern for use on a data storage surface that includes at least one track to minimize position error during positioning of a transducer over the data storage surface. The servo pattern includes a plurality of servo burst fields of constant amplitude for defining a centerline of the track and for determining the position of the transducer. According to the present invention, at least one servo burst field comprises N segments, where N.gtoreq.2, and each of the N segments is written with constant amplitude. The amplitude of the at least one servo burst field is then determined as a function of the amplitudes of the N segments.

Abstract: A method and apparatus for improving baseline recovery of an MR head using a programmable AC coupling pole. The location of the pole may be adjusted to achieve the fastest recovery from a baseline shift without degrading the normal channel performance. Further, the pole may be moved during the data recovery procedure to recover from a data read error. The programmable AC coupling pole includes a circuit path carrying digital data signals read from a recording media by a magnetic head, an amplifier coupled to the circuit path for amplifying the digital data signals, and a recovery time setting means having an programmable recovery time constant associated therewith. Once a data read error has been detected by the system, the recovery time constant may be adjusted to set a recovery time for the amplifier to provide readable data signals.

Abstract: A data recording disk drive uses a circuit responsive to the removal of power to the spindle motor to generate a two-stage torque to retract the actuator and move it to a parking ramp. The spindle motor power removal circuit sends an initial signal to a first switch connected to a full-wave rectifier retract circuit and, after a predetermined delay time, a second signal to a second switch also connected to the rectifier circuit. Activation of the first switch causes only a portion of the available current from the spindle motor windings to reach the actuator, so that the actuator is moved with an initial low-level torque which is sufficient to bring the actuator to the disk OD of the disk under all circumstances. Activation of the second switch a predetermined delay time later allows all available current to reach the actuator so the actuator is then moved with a high-level torque which is sufficient to properly park the sliders on the load/unload ramp under all conditions.

Abstract: A control algorithm compensates for a bias force disturbance and a runout disturbance of an actuator by means of a state feedback to decrease the number of the design parameters, thereby simplifying the design process. A compensation system for the disturbances includes a state variable calculating device for receiving a discrete feedback input signal representative of an actual position of a magnetic head mounted on a front end of the actuator, so as to generate state variables; a differentiating device for differentiating the discrete feedback input signal to generate a velocity signal; and a state feedback control device for receiving the state variables, the velocity signal and the discrete feedback input signal, so as to generate a discrete control input signal to be applied to the actuator.

Abstract: Device and method for restoring data in a digital VCR is disclosed in which redundancy is provided for detection of more reliable user data. The device optimally equalizes data reproduced in the VCR, and employs comparison detection in restoring the equalized data at the present time. This is accomplished by comparing the equalized data, at the present time, to either an even series prior data or an odd series prior data which has passed through the equalizing part. Determination of the data, at the present time, as not being of a positive polarity where the prior data is determined to be of a positive polarity and determination of the data, at the present time, as not being of a negative polarity where the prior data is determined to be of a negative polarity, thereby prevents the wrong determination applied to the above determination result in restoring the data to the present time.

Abstract: An apparatus for recording an information signal on a record carrier where the record carrier has a first and a second tracking signal of specific frequencies and wavelengths. The tracking signals are recorded in respective first and second tracks which run parallel to each other in their longitudinal direction on the record carrier. The apparatus is provided With a receiver for receiving the information signal, and a converter for converting the information signal into a channel signal. The channel signal includes signal blocks of information with each signal block including a portion of the information signal. A writing head writes the channel signal in a third track on the record carrier. A reading head is adapted to read at least one of the first and second tracking signals from the first and second tracks. A generator generates a control signal from the at least first and second tracking signals read from the record carrier.

Abstract: A multiple-gap head for transferring data to or from a storage medium is disclosed. Data read by the gaps are directed over a plurality of serial data paths where the data are processed and synchronized. In some embodiments, all or part of a data synchronizer is shared by the serial data paths. The data are then assembled into a parallel data stream for delivery to a computer. Reading the data simultaneously with multiple gaps increases by several times the rate at which data can be transferred to or from a storage medium. In accordance with another aspect of the invention, a three-gap head is provided to reduce or eliminate the cross-talk or noise fringe problems which reduce the track density in a storage medium. A signal attenuator and a signal inverter are connected to each of the side gaps and the outputs thereof are summed with the signal originating at the center gap, such that the inverted signals from the side gaps cancel any cross-talk originating at the center gap.

Abstract: A pre-read learning digital servo-control device has a digital servo-control device for controlling the speed and/or position of a controlled object. A corrective control input for a (n+1)-th trial for state control is based on errors observed in the n-th trial. The corrective control input is applied at m sample time(s) before the time when a subsequent error is observed, where m is an integer greater than or equal to one for a sampling time of the digital servo-control device.

Abstract: A high-density disk unit and disk medium are disclosed. Track ID information is not placed in a servo area, or if some track ID information is placed therein, a necessary minimum is placed. The servo area is thus reduced in order to improve formatting efficiency.A data side of a disk medium is divided into a servo area and a data area in units of a sector. A track ID area in which track information is recorded is defined at the start position of the data area immediately following the servo area. A formatter circuit allows a write data modulation circuit to write track information in the track ID area during track formatting. For writing in the data area, the formatter circuit allows a read data demodulation circuit to read data from the track ID area. Track information is thus detected, and writing tracking is assured.

Abstract: A magnetic disc storage system employing two stage actuators for simultaneously positioning recording heads over the top and bottom surfaces of the disc is disclosed. The recording heads are fastened to a distal end of respective top and bottom load beams. A base end of the load beams is connected to a voice coil motor (VCM) rotary actuator which simultaneously positions both recording heads over the disc. A silicon microactuator is also fastened to the distal end of at least one of the load beams for positioning the recording heads independent of one another, thereby allowing simultaneous tracking of embedded servo data. Various data formats are provided, including interleaving logical sector numbers, symbols of a logical sector, and segments of a logical sector, between the top and bottom physical sectors of a track.

Abstract: A read/write circuit detects the occurrence of a thermal asperity in accordance with data read from a disk. Thermal asperity status register sets a flag corresponding to thermal asperity occurrence spot in a servo area. A write/read fault generator outputs no WRF signals if the corresponding flag of the thermal asperity status register is set even when error detection is notified from an address error register, and thereby enables a sequencer to continue its recording and reproducing operation.

Abstract: A sampled amplitude read channel is disclosed for disk storage systems which asynchronously samples an analog read signal, adaptively equalizes the resulting discrete time sample values according to a target partial response, extracts synchronous sample values through interpolated timing recovery, and detects digital data from the synchronous sample values using a Viterbi sequence detector. To increase the speed of the read channel, the FIR filters in the equalizer and interpolator are implemented according to a residue number system. Further, the residue number system implementation of the FIR filters uses "one-hot" encoding to decrease power dissipation.

Abstract: The present invention relates to a method and apparatus for the measurement of defects in magnetic recording disks using a logarithmic amplifier. A magnetic head senses a magnetic field of a magnetic disk and creates a read signal having a varying amplitude. The test apparatus has a squarer which receives and squares the read signal. A logarithmic amplifier coupled to the squarer converts the squared signal to a logarithmic signal. The logarithmic signal is filtered by a first filter. A second filter coupled to the logarithmic amplifier provides an average of the peaks of the logarithmic signal. A digital-to-analog converter coupled to the second filter scales the output of the second filter. The test apparatus further comprises a comparator having a first input and a second input, where the first input is coupled to the first filter, and the second input is coupled to the digital-to-analog converter.