Texas Instruments Corporation

Charles H Sobey

Echere Iroaga

According to a broad aspect of the invention, a method and apparatus are presented for identifying a track ( ) of a rotating disk ( ) of a mass data storage device ( ), using EPR4 data detection techniques. The track identification indicia ( ) may be written more densely than the track identification indicia would have been written without using EPR4 data equalization techniques, wherein track identification indicia pulses ( ) may at least partially overlap. The identification indicia ( ) is read from the disk ( ) using a read head ( ), and processed using EPR4 data equalization techniques in an EPR4 Viterbi detector ( ). The Viterbi detector ( ) may be used also to detect data pulses ( ) by switching its mode of operation from a track identification mode to a data detection mode.

Method and apparatus for identifying a track of a rotating disk using EPR4 data equalization and detection techniques

A method and apparatus for characterizing a magnetic disk ( ) of the type that contains data to be read by a magneto-resistive type head ( ) in proximity thereto is disclosed. The method includes writing a continuous signal onto the disk, and reading back the signal written onto the disk ( ) using the magneto-resistive type head ( ). The read back signal is compared to a threshold value ( ), and areas of said disk at which energy contained in said read back signal occurs above said threshold value ( ) are mapped. The energy content is measured by accumulating oversampled signal values from the read back signal during a time at which said read back signal exceeds the threshold value ( ).

Apparatus for measuring and characterizing thermal asperities in a mass data storage device

A method and apparatus for characterizing asymmetries of a magneto-resistive type head in proximity to a magnetic media such as a magnetic disk of a hard disk drive. The method includes using the magneto-resistive type head to read a continuous signal from the magnetic media to provide a read back signal. Energies contained in the read back signal which occur in excess of a predetermined threshold for the positive and negative portions of the read back signal are then determined. The energies may be determined by accumulating sampled signal values from the read back signal in registers during times at which the read back signal exceeds the threshold.

Method and apparatus for characterizing asymmetries of an MR head

A method and apparatus for identifying a track ( ) of a rotating disk ( ) of a mass data storage device ( ) uses EPR4 data detection techniques. The values of the encoded track identification indicia are selected so that they have a distance between any two track identification codewords that is larger than the minimum distance of the codeset from which they were selected. The identification indicia ( ) are read from the disk ( ) using a read head ( ), and processed using EPR4 data equalization techniques in an EPR4 Viterbi detector ( ). The Viterbi detector ( ) may have a trellis in which data paths of minimum distance of the codeset from which the track identification indicia ( ) were selected do not exist. The Viterbi detector ( ) may be used also to detect data pulses ( ) by switching its mode of operation from a track identification mode to a data detection mode.

Trellis encoding and decoding of track identification indicia

A hard disk drive system (10) includes a read head (21) for reading information from a rotating magnetic disk (12). The read head outputs a servo burst signal in response to servo information (59) on the disk. An analog-to-digital converter (33) is provided to oversample the servo burst signal during each of a plurality of successive time intervals, in order to obtain a plurality of samples for each such time interval. An accumulator (74) is provided to sum the samples for each time interval, in order to obtain for each time interval a respective accumulation value that represents an integration of the burst signal for that time interval. A filtering circuit (86) is provided to determine a burst value for the servo burst signal, by applying a filtering function to a set of the accumulation values. The filtering function may involve determining a median accumulation value from the set of accumulation values, or determining a mean of the accumulation values in the set.

Method and apparatus for demodulating a servo burst signal in a hard

A detection device for detecting a pattern and determining valid patterns by a series of tests. These tests include rejecting patterns based on minimum Hamming distance, spectral energies that are not concentrated with a predetermined ideal spectrum, that are not valid predetermined valid codewords, patterns that are not anti-symmetric and that have closest transition spacing.

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Plano, TX, United States of America

Charles H Sobey