Maxtor Corporation

Curtis W Egan

Steve McCarthy

Bruce A Liikanen

Gang Herbert Lin

Quinn Jay Haddock

Christine Green

David Finamore

David Winters

A method and apparatus for compensating for repeatable runout using wide embedded runout correction fields is provided. In one embodiment, a disk surface is provided with a write head associated therewith. The disk surface has a data track having a width. An embedded runout correction (ERC) field is written onto the disk surface, wherein the ERC field has a width that is greater than the width of the data track.

Method and apparatus for compensating for repeatable runout using wide embedded runout correction fields

Methods and structures for detecting touchdown of the read/write head on its recording surface or for detecting other read signal amplitude modulations as proportional to variance of the value of the read channel variable gain amplifier ('VGA'). Variance in the VGA values caused by the standard feedback control electronics associated therewith is proportional to amplitude modulations of the sensed signal picked up by the read channel (or servo read sensor). These amplitude modulations are, in turn, reflective of flying height of the read/write head as well as generally indicative of other parameters of the read channel operation. Touchdown of the read/write head and other parameters of the disk drive operation may therefore be detected as variances in the VGA control values.

Methods and structure for detecting anomalous events in a disk drive using VGA variance

Methods and structures for a general purpose, discrete time sample, interval accumulating filter for measuring any of a plurality of parameters associated with operation of a digital read channel. The general purpose interval accumulating features and aspects hereof permit flexible configuration for measuring a variety of operational characteristics and parameters of a digital, discrete time sample, read channel. The interval accumulating filter may sense harmonic frequencies associated with mechanical and electrical noise in the read channel operation. Other features and aspects hereof permit monitoring of multiple signal frequencies of a read channel in a disk drive, error recovery of a bad sector in a disk drive, and measurement of numerous other operational aspects of a discrete time digital sample read channel.

Methods and structure for general purpose interval accumulating filter for measuring operational parameters of a digital read channel

Detecting flaws in a disk drive includes sampling a read signal provided by reading a data pattern from a disk to obtain samples, obtaining significant samples from the samples, deriving a value from the significant samples, and reporting a flaw if a comparison between the derived value and a threshold value is unacceptable.

Flaw detection in disk drive using significant samples of data pattern stored on disk

A method and apparatus for detecting flaws requiring sparing of portions of storage media included as part of a hard disk drive are provided. A window of a selected portion of the storage medium is formed, and the density of defects detected within that window is calculated. If the density of defects exceeds a threshold amount, a signal is passed to the controller. The portion of the storage media containing the defects that caused the generation of the flag may then be spared. The present invention allows the potential for detected defects to significantly affect the ability of the storage medium to be assessed. Furthermore, the present invention does not require that the location of each defect be stored in memory. Accordingly, the present invention is economical to implement, and allows defects to be assessed in substantially real time and with improved accuracy.

Method and apparatus for identifying defective areas on a disk surface of a disk drive based on defect density

Tools are provided to identify undesired pole tip protrusion (PTP) on a write portion of a read/write head in a hard disk. Such tools may be incorporated in the hard disk. A corrective action arrangement performs a corrective action in response to the identification of an undesired pole tip protrusion. The corrective action may comprise burnishing of pole tips of a write portion of the read/write head. An asperity read signal condition monitoring circuit monitors asperity conditions from the read signal. The asperity condition may be a high fly write condition, or it may be a thermal asperity condition. A PTP determining circuit determines when a monitored condition is indicative of an undesired PTP condition. A PTP test write cycle may be caused, during which the monitoring circuit monitors either during or right after the PTP test write cycle.

Monitoring of phenomena indicative of PTP in a hard disk and controlling the burnishing of heads

A method for allocating tracks into servo sector zones in a disk drive such that each zone has an equal range of channel bit densities is provided. In addition, a disk drive having servo sector zones that each have an equal range of channel bit densities is provided. According to the method and apparatus of the present invention, servo sector zones are sized such that the range of servo sector channel bit densities encompassed by each zone is constant from zone to zone. By constraining the range of channel bit densities encompassed by the servo sector zones, the equalization or conditioning of signals derived from the servo sectors can be optimized for a given number of zones. Accordingly, the method and apparatus of the present invention increases the accuracy with which servo sector data is detected while decreasing the complexity of the detector circuit.

Method and apparatus for improving servo zoning for PRML detected gray code using channel bit densities

A disk drive that monitors changes in flying height is disclosed. In one embodiment, the disk drive includes a disk for storing information and an air bearing slider with a transducer that includes a write element for writing information to the disk during a write operation and a magneto-resistive (MR) read element for reading information from the disk during a read operation. The MR read element generates a readback signal during the write operation that includes a thermally induced signal caused by thermal changes in the MR read element and a magnetically induced signal caused by magnetic flux applied by the write element to the MR read element. The thermally induced signal has a relatively low frequency content and the magnetically induced signal has a relatively high frequency content. The disk drive also includes a low pass filter for receiving the readback signal and isolating the thermally induced signal from the magnetically induced signal, a threshold detector for receiving the thermally induced signal from the filter and generating a high fly write detection signal when the thermally induced signal exceeds a threshold value, and a controller for modifying the write operation in response to the high fly write detection signal.

Disk drive that monitors the flying height of a dual element transducer using a thermally induced signal during write operations

A byte wide flaw scan interface is used to identify an characterize flaws in a disk medium. In one embodiment, the associated disk drive ( ) includes head electronics ( ) associated with a disk drive controller ( ) via an NRZ interface ( ). The NRZ interface ( ) is operative for transmitting flaw information for a particular disk address via 8 predefined bit lines. The bit lines have separate definitions for user data sector addresses and servo wedge addresses. By using this byte wide interface, media flaws of various types can be identified and characterized based on a single pass of the transducer head over the disk surface thereby shortening testing times.

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Thornton, CO, United States of America

Curtis W Egan