Abstract: Embodiments of the present disclosure provide a method including recording time stamps for a repeating characteristic of a spindle back electromotive force (BEMF) signal and comparing one or more of the recorded time stamps for the repeating characteristic of the spindle BEMF signal with an expected value for the one or more recorded time stamps to detect a timing error associated with writing a servo pattern on a machine readable medium of a self-servo write (SSW) system. Other embodiments may be described and/or claimed.

Abstract: Various embodiments of the present invention provide systems and methods for data processing. As an example, a pattern detection circuit is discussed that includes a distance calculation circuit and a comparator circuit. The distance calculation circuit is operable to calculate a noise whitened distance between a reference signal and a received input to yield a comparison value. The comparator circuit is operable to compare the comparison value with a threshold value.

Abstract: According to one embodiment, a magnetic disk includes a plurality of tracks each having a plurality of servo frames with servo burst data and repeatable runout correction data written thereto. The repeatable runout correction data includes a pattern repeated at a predetermined period and is written so that beginning of write is delayed by a time corresponding to a correction amount with respect to a base point corresponding to a synchronization timing position in the servo frame. A detector detects a phase delay amount corresponding to a time elapsed until the repeated pattern is read from the servo frame by a magnetic head, with respect to the synchronization timing position.

Abstract: Various embodiments of the present invention provide systems and methods for data processing. For example, a data processing circuit is discussed that includes: a data detector circuit, a low latency detection circuit, and an error calculation circuit. The data detector circuit is operable to perform a data detection process on a first signal derived from a data input to yield a detected output, and to provide a loop error as a difference between the detected output and the first signal. The low latency detection circuit operable to process a second signal derived from the data input to yield a fast detector output, and to provide a generated error as a difference between the fast detector output and the second signal. The error calculation circuit is operable to calculate an error value based at least in part on the generated error and the loop error.

Abstract: The present inventions are related to systems and methods for transferring information to and from a storage medium, and more particularly to systems and methods for positioning a sensor in relation to a storage medium. For example, an apparatus for determining a sensor position is disclosed that includes discrete Fourier transform calculators operable to process input data to yield a magnitude response of the input data at each of a number of candidate frequencies, a comparator operable to compare the magnitude responses to yield a winning candidate frequency, a servo controller operable to process at least one servo field in the input data to identify a position of a sensor based on the at least one servo field, and a servo frequency synthesizer operable to establish a frequency of operation in the servo controller based at least in part on the winning candidate frequency.

Abstract: The present invention realizes reduction of position information demodulation errors caused by the eccentricity of the magnetic disk and improvement of position signal detection accuracy, as well as enabling quick eccentricity clock correction for arbitrary clock frequencies. An inspection device in accordance with the present invention comprises: a servo demodulation unit which demodulates servo information; a PLL clock generating unit which generates a reference clock and supplies the reference clock to the servo demodulation unit; and a tester control unit. The PLL clock generating unit includes an eccentricity correction circuit for correcting the frequency of the reference clock depending on the eccentricity of the magnetic disk. The tester control unit generates correction data for correcting the frequency of the reference clock, multiplies the correction data by the inverse of a transfer function of the PLL clock generating unit, and supplies the product to the eccentricity correction circuit.

Abstract: A disk drive is disclosed comprising a disk comprising a plurality of servo tracks, wherein each servo track comprises a plurality of servo sectors, and a head actuated radially over the disk, wherein the head comprises a read element separated from a write element by a reader/writer gap. The head is positioned over a first servo track, and a clock is synchronized to servo data in first and second servo sectors of the first servo track. A first phase-offset of the clock is measured for the first servo sector, and a second phase-offset of the clock is measured for the second servo sector, wherein the first and second phase-offset correspond to an end of the reader/writer gap at the first servo track. The first and second phase-offset are averaged to generate an average phase-offset for the first servo track.

Abstract: Methods and apparatus are provided for detection of a synchronization mark based on a position of an extreme distance metric. A synchronization mark is detected in a received signal by computing a distance metric between the received signal and an ideal version of the received signal expected when reading the synchronization mark, wherein the distance metric is computed for a plurality of positions within a search window; determining a substantially extreme distance metric within the search window; and detecting the synchronization mark based on a position of the substantially extreme distance metric. The distance metric can comprise a sum of square differences or a Euclidean distance between the received signal and the ideal version of the received signal.

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of servo sectors defining a plurality of servo tracks. The servo tracks form a plurality of servo zones. A disk locked clock is synchronized relative to a servo data rate of the servo zone the head is over. A first reader/writer gap is measured in cycles of the disk locked clock at a first servo track in the first servo zone. A second reader/writer gap is measured in cycles of the disk locked clock at a second servo track in the second servo zone. The first and second reader/writer gaps are normalized to generate a normalized first and second reader/writer gaps. A third reader/writer gap is estimated in cycles of the disk locked clock at a third servo track in the second servo zone based on the normalized first and second reader/writer gaps.

Abstract: A hard disk drive system includes a first channel module and a second channel module. The first channel module is configured to receive a first data from or transfer the first data to a first amplifier module of a hard disk assembly when reading from or writing to a first surface of a disk of the hard disk assembly. The second channel module is configured to receive a second data from or transfer the second data to a second amplifier module of the hard disk assembly when reading or writing to a second surface of the disk while the first channel module receives the first data from or transfers the first data to the first amplifier module.

Abstract: A motor drive device has a driver circuit generating an output current for a motor and a control circuit controlling the drive circuit. The control circuit, when switching the driver circuit from a PWM-driving state to a linear-driving state, controls the timing of the switching such that the path of the output current does not change between before and after the switching, and in addition, in the middle of the switching, switches the driver circuit to a high-output-impedance state momentarily.

Abstract: An assembly and method to determine adjacent track coherence is disclosed. The assembly includes coherence circuitry configured to receive phase and frequency offsets from timing recovery circuitry and determine an inter-track phase and frequency coherence between the encoded data on a first track and the encoded data on a second track adjacent to the first track utilizing the frequency and phase offsets from the timing recovery circuitry for the output signals corresponding to the first and second tracks.

Abstract: A thin film magnetic recording head is fabricated by forming a substrate from opposing ferrite blocks which have a ceramic member bonded between them. This structure is then diced to form a plurality of columns, wherein each column has a ferrite/ceramic combination. Each column represents a single channel in the completed head. A block of ceramic is then cut to match the columned structure and the two are bonded together. The bonded structure is then cut or ground until a head is formed, having ceramic disposed between each channel. A ferrite back-gap is then added to each channel, minimizing the reluctance of the flux path. The thin film is patterned on the head to optimize various channel configurations.

Abstract: A system including a mark module, an estimation module and an adjustment module. The mark module is configured to generate a first indicator for a first mark on a storage medium detected when first servo data is read from the storage medium, and a second indicator for a second mark on the storage medium detected when second servo data is read from the storage medium. The estimation module is configured to, based on i) a first location of a center of the storage medium about which the storage medium is rotated, and ii) a period between times when the first indicator and the second indicator are generated, estimate a first distance or an offset angle relative to the first location. The adjustment module is configured to, based on the first distance or the offset angle, adjust a sampling frequency at which user data is read from the storage medium.

Abstract: A shingled magnetic recording (SMR) hard disk drive (HDD) essentially eliminates the effect of far track erasure (FTE) in the boundary regions of annular data bands caused by writing in the boundary regions of adjacent annular data bands. The extent of the FTE effect is determined for each track within a range of tracks of the track being written. Based on the relative FTE effect for all the tracks in the range, a count increment (CI) table or a cumulative count increment (CCI) table is maintained for all the tracks in the range. For every writing to a track in a boundary region, a count for each track in an adjacent boundary region, or a cumulative count for the adjacent boundary region, is increased. When the count reaches a predetermined threshold the data is read from that band and rewritten to the same band.

Abstract: The present disclosure includes systems and techniques relating to control of magnetic recording devices, such as disk drives. A recording device can contain a medium that includes data tracks disposed on discrete strips of magnetic material that are arranged based on circumferences of the medium. The medium can include servo regions disposed on discrete strips of magnetic material that are arranged based on radii of the medium and extend from an inner diameter of the medium to an outer diameter of the medium.

Abstract: According to one embodiment, a disk storage device includes: a disk on which a servo pattern is recorded; a head; a driver; a signal generator; a demodulator; and a controller. Position signals for detecting an offset position from a center of a track are recorded in a recording area of a servo pattern. The signal generator generates a first timing signal indicating a timing for reading the position signals. When the controller performs a seek operation for moving the head to a target track, the signal generator generates a second timing signal. The period of the second timing signal for reading each of the position signals is made shorter than that of the first timing signal. A center time of the period of the second timing signal is shifted closer to a demodulation center time corresponding to a center of the recording area than that of the first timing signal.

Abstract: A variable latency interface and method for managing variable latency. An apparatus includes a storage device controller and a read/write channel coupled to the storage device controller by a variable latency interface. The variable latency interface includes a media control component configured for read and write operations. The variable latency interface also includes a data transfer component configured for read and write operations. A read or write operation in the media control component is offset from a respective read or write operation in the data transfer component by a latency period.

Abstract: According to one embodiment, a disk storage device includes: a disk on which a servo pattern is recorded; a head; a driver; a signal generator; a demodulator; and a controller. Position signals for detecting an offset position from a center of a track are recorded in a recording area of a servo pattern. The signal generator generates a first timing signal indicating a timing for reading the position signals. When the controller performs positional control along a virtual circular orbit of the disk, the signal generator generates a second timing signal. The period of the second timing signal for reading each of the position signals is made shorter than that of the first timing signal. A center time of the period of the second timing signal is shifted closer to a demodulation center time corresponding to a center of the recording area than that of the first timing signal.

Abstract: Writing servo wedge code to a disk is disclosed. A wedge-to-wedge time interval is determined. At least until it is determined that a lock criterion is met: For each wedge-to-wedge time interval, a wedge frequency error is computed based on an adjustable clock. The clock is adjusted based on one or more of the wedge frequency errors. It is determined whether a lock criterion is met based on one or more of the wedge frequency errors. After the lock criterion is met, servo wedge code is written to the disk.

Abstract: A disk drive is disclosed comprising a disk having a plurality of data tracks, and a head actuated over the disk, the head comprising a first read element and a second read element. A data track is read to generate a first read signal emanating from the first read element and a second read signal emanating from the second read element. The first read signal is delayed in continuous time relative to the second read signal to generate a delayed read signal, and the second read signal is combined with the delayed read signal to generate a combined read signal. An estimated data sequence is detected from the combined read signal.

Abstract: An apparatus includes a disk arrangement, a first signal processing path configured to output data from the disk arrangement according to a first protocol, a second signal processing path configured to output data from the disk arrangement according to a second protocol, and an interface including a set of electrical conductors and a mode control unit. The mode control unit is configured to output data from the first signal processing path on the set of electrical conductors according to the first protocol and to output data from the second signal processing path on the set of electrical conductors according to the second protocol according to a control signal received by the mode control unit. The second protocol is different from the first protocol.

Abstract: The present disclosure includes systems and techniques relating to control of magnetic recording devices, such as disk drives. A described technique includes producing signals that include a write clock signal and a servo clock signal, processing a waveform produced by a read head operated with respect to a recording medium, which includes magnetic bit cells arranged on tracks, and the servo clock signal. The technique includes producing, based on the waveform, a servo detect pulse that indicates a detection of servo data, measuring a timing difference that is based on the servo detect pulse and a write pulse of the write clock signal, and controlling an adjustment of a phase of the write clock signal based on the timing difference to align the write clock signal with at least a portion of the bit cells.

Abstract: The present disclosure includes systems and techniques relating to control of magnetic recording devices, such as disk drives. A described technique includes receiving a waveform produced by a read head operated with respect to a recording medium and a servo clock signal. A medium can include magnetic data bit cells, a first servo wedge, a second servo wedge, and phase tracking fields, where at least a portion of the phase tracking fields are arranged between the first servo wedge and the second servo wedge. The servo wedges can include respective servo sync marks. The technique includes producing, based on the waveform, a servo detect pulse that indicates a detection of a servo sync mark. The technique includes controlling a first adjustment of a phase of a write clock signal, the first adjustment being responsive to the servo detect pulse. The technique includes producing, based on the write clock signal, samples of the waveform that correspond to phase tracking fields.

Abstract: A hard disk drive or other disk-based storage device comprises a storage disk, a read/write head configured to read data from and write data to the disk, and control circuitry coupled to the read/write head and configured to process data received from and supplied to the read/write head. The control circuitry comprises calibration circuitry configured to vary a phase of a clock signal as a test pattern is written to the storage disk as part of a calibration procedure, and disk locked clock circuitry coupled to the calibration circuitry and configured to obtain phase lock between the clock signal and a timing pattern on a surface of the storage disk. The calibration circuitry is further configured to determine an initial phase update value to be applied by the disk locked clock circuitry in a control loop as the phase of the clock signal is varied as part of the calibration procedure.

Abstract: A method and apparatus for generating a laser signal for driving a laser used in thermal-assisted recording. A channel of a hard drive generates a high-frequency component of the laser signal—e.g., a periodic wave or series of pulses—and synchronizes the phase of the laser signal with a corresponding write data signal which controls the magnetization of data bits within the magnetic disk of the hard drive. The channel may be connected to a read/write integrated circuit via a channel interconnect. The read/write circuit may include a second phase control to compensate for any phase shift and an adder circuit to combine the transmitted high-frequency laser with a DC bias. Further, the read/write circuit may include a feedback loop for adjusting the DC bias based on environmental parameters of the hard drive such as temperature.

Abstract: In an embodiment of the present invention, a disk drive comprises a head actuated over a disk including a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The read signal from the head is processed to detect a plurality of the sync marks in spiral track crossings. A plurality of timing recovery measurements are generated corresponding to the detected sync marks, and the timing recovery measurements are biased based on a radial location of the head. A servo write clock is generated in response to the biased timing recovery measurements, and the servo write clock is used to write product servo sectors to the disk.

Abstract: Various embodiments of the present invention provide systems and methods for data processing. As an example, a data processing circuit is discussed that includes: a servo address mark count circuit, a user sync mark count circuit, and an offset calculation circuit. The servo address mark count circuit is operable to provide: a first count corresponding to a first servo address mark within a first track of a storage medium, a second count corresponding to a second servo address mark within the first track, a third count corresponding to a third servo address mark within a second track of the storage medium, and a fourth count corresponding to a fourth servo address mark within the second track. The user sync mark count circuit is operable to provide: a fifth count corresponding to a first user sync mark within the first track, and to provide a sixth count corresponding to a second user sync mark within the second track.

Abstract: According to one embodiment, a magnetic disk includes a plurality of tracks each having a plurality of servo frames with servo burst data and repeatable runout correction data written thereto. The repeatable runout correction data includes a pattern repeated at a predetermined period and is written so that beginning of write is delayed by a time corresponding to a correction amount with respect to a base point corresponding to a synchronization timing position in the servo frame. A detector detects a phase delay amount corresponding to a time elapsed until the repeated pattern is read from the servo frame by a magnetic head, with respect to the synchronization timing position.

Abstract: According to one embodiment, there is provided an information recording apparatus that writes information onto a magnetic recording medium including a plurality of fine magnetic grains. The information recording apparatus includes a random number generation unit, a modulation unit, and a processing unit. The random number generation unit generates a random number bit value. The modulation unit modulates a period of a basic clock according to the random number bit value generated, and generates a modulated clock. The processing unit writes or reads information with respect to the magnetic recording medium in synchronization with the modulated clock generated.

Abstract: According to one embodiment, a signal processing circuit processes a signal read from a magnetic disk including a servo region and a user data region, the servo region including a servo address mark, the user data region including a data sector, and includes a counter and a gate controller. The counter is configured to count a first clock when having detected the servo address mark based on the signal read from the magnetic disk. The gate controller is configured to generate a pulse for locating the data sector in synchronization with a second clock when the counter counts a first value.

Abstract: The present disclosure includes systems and techniques relating to control of magnetic recording devices, such as disk drives. Systems and techniques include generating timing data based on a clock signal and a waveform produced by a head operated with respect to a rotating recording medium and the clock signal, determining model parameters based on the timing data to model deterministic disturbances associated with the rotating recording medium, predicting a frequency offset by a model-based technique for the compensation of the deterministic disturbances between two servo wedges, predicting a frequency offset associated with one or more nondeterministic disturbances by a loop filter, determining a clock adjustment based on the predicted deterministic and nondeterministic frequency offsets, and adjusting a clock frequency to read or write data within the area.

Abstract: A write clock generator for use in writing data to a rotating patterned magnetic media disk is disclosed. The generator includes a magnetic read head for generating a succession of servo signals representative of succession of servo magnetization patterns detected from a corresponding succession of arcuate sectors along a circular data track on the disk. A preamble processor generates a corresponding succession of sector pair signals representative of the lengths of adjacent sectors along the data track on a rolling pair-wise basis. A next sector length predictor processor determines for a succession of pairs of sectors, a length ratio of the lengths of the sectors in the respective pairs of sectors.

Abstract: Data storage systems are provided. Data storage systems illustratively include a writing element and a recording medium. In some embodiments, the writing element generates first and second magnetization fields that respectively record first and second magnetization patterns to the recording medium. In some embodiments, the writing element is de-saturated between recording the first and second magnetization patterns.

Abstract: A method for randomizing data to mitigate false VFO detection is described. In one embodiment, such a method includes simultaneously receiving multiple input data streams. Each input data stream is associated with a different track on a magnetic tape medium. The input data streams are simultaneously scrambled to produce multiple randomized data streams. The input data streams are scrambled such that different bit patterns are produced in the randomized data streams even where corresponding bit patterns in the input data streams are identical. The randomized data streams are simultaneously written to their associated data tracks on the magnetic tape medium.

Abstract: Methods and systems for adaptively equalizing an analog information signal for a signal path, including sampling the analog information signal, thereby generating analog samples, and performing an equalizing process on the analog samples, wherein the equalizing includes processing an average of post-transition sample amplitudes and an average of steady state sample amplitudes of the analog samples to produce equalized analog samples.

Abstract: Various embodiments of the present invention provide apparatuses, systems and methods for data detection in a detector with a pruning control system. For example, a data detector is disclosed that includes a first set of counters operable to distinguish prunable data from non-prunable data in the data detector, a second set of counters operable to generate initial values for the first set of counters, and a prune control signal generator operable to generate a prune control signal based on the first set of counters. The second set of counters is operable to generate the initial values at least in part before a syncmark is detected in a data sector. The initial values are used to initialize the first set of counters when the syncmark is detected in the data sector. The prune control signal controls whether the data detector is allowed to prune a trellis.

Abstract: Various embodiments of the present invention provide systems, methods and media formats for efficiently determining a position error of a head in relation to a storage medium. In one case, a system is disclosed that includes a storage medium with a series of data. The series of data includes a first defined marker and a second defined marker located a distance from the first defined marker, and position location data. The systems further include a first detector circuit that is operable to detect the first defined marker and to establish a location of the first defined marker, and a second detector circuit that is operable to detect the second defined marker and to establish a location of the second defined marker. The systems further include an error calculation circuit and an interpolation circuit. The error calculation circuit is operable to calculate an interpolation offset based at least in part on the location of the first defined marker and the location of the second defined marker.

Abstract: A disk drive is described that uses a vibration sensor to generate a compensating feed-forward control signal to synchronize the write clock frequency with the modulated data island frequency. A linear vibration sensor is positioned with its sensitivity axis aligned with the tangential direction of a track at the radial position of the write head. The tangential component of the external linear vibration is measured by the sensor. The feed-forward control signal derived from the linear vibration sensor modifies the control voltage input to VCO (voltage controlled oscillator) in the write clock generator to adjust the write clock frequency to compensate for the modulated data island frequency caused by the tangential component of the linear vibration.

Abstract: A write clock generator for use in writing data to a rotating patterned magnetic media disk is disclosed. The generator includes a magnetic read head for generating a succession of servo signals representative of succession of servo magnetization patterns detected from a corresponding succession of arcuate sectors along a circular data track on the disk. A preamble processor generates a corresponding succession of sector pair signals representative of the lengths of adjacent sectors along the data track on a rolling pair-wise basis. A next sector length predictor processor determines for a succession of pairs of sectors, a length ratio of the lengths of the sectors in the respective pairs of sectors.

Abstract: Various embodiments of the present invention provide systems and methods for locating a reference pattern on a storage medium. For example, various embodiments of the present invention provide systems for locating a reference pattern on a storage medium. Such systems include a sliding window phase calculator circuit, a delay circuit and a mark detector circuit.

Abstract: A system to interface analog-to-digital converters to inputs with arbitrary common-modes includes a common-mode voltage amplifier circuit and a PGA circuit connected to the common-mode voltage amplifier circuit. The common-mode voltage amplifier and PGA circuits receive first and second analog input signals. The PGA circuit eliminates the arbitrary common-modes from the first and second analog input signals based on an output of the common-mode voltage amplifier circuit.

Abstract: A hard disk drive or other disk-based storage device comprises a storage disk, a read/write head configured to read data from and write data to the storage disk, and control circuitry coupled to the read/write head and configured to process data received from and supplied to the read/write head. The control circuitry comprises clock adjustment circuitry configured to generate a control signal for adjusting a parameter of a clock signal based at least in part on timing information obtained by detecting a timing pattern on a surface of the storage disk. The control signal is generated utilizing at least a predictive correction control loop, with the clock adjustment circuitry comprising predictive control firmware that implements at least a portion of the predictive correction control loop.

Abstract: According to embodiments of the present invention, a method for demodulating a position error signal from a readback servo signal having a first frequency associated with a first servo track of a storage medium and a second frequency associated with a second servo track adjacent to the first servo track is provided. The method includes sampling the readback servo signal at successive time instants to provide a sequence of samples, computing a Discrete Fourier Transform based on the sequence of samples, and providing a measurement indicative of the position error signal based on the Discrete Fourier Transform. According to further embodiments of the present invention, a demodulator is also provided.

Abstract: One aspect of the embodiment utilizes a servo frame interval correction apparatus which includes a detection unit for detecting a first servo frame formed on said recording medium. The apparatus includes an acquiring unit acquiring a detection time interval between said first servo frame and a second servo frame detected subsequently to the first servo frame from a table storing a detection time interval between a specific servo frame and a servo frame detected subsequently to the specific servo frame. The apparatus includes a differential calculation unit calculating a differential between the detection time interval acquired by said acquiring unit and a reference time interval; and a correction unit correcting an estimated position of said second servo frame based on the differential calculated by said differential calculation unit.

Abstract: There is disclosed a method and apparatus for measuring a signal using a measurement system. The signal has a frequency component that is to be detected by the measurement. The frequency component has a varying phase. The signal has at least one interruption thereto. The method includes: processing the signal with the measurement system to detect the frequency component in the signal and stalling the measurement system before the start of the interruption. The stall period is calculated such that the processing of the signal is resumed: i) after the end of the interruption, and ii) where there is substantially no discontinuity between the phase of the frequency component in the signal at the end of the stall and in the phase of the frequency component in the signal at the beginning of the stall.

Abstract: Preamble fields are written on a storage disk in a hard disk drive in a way that reduces track squeeze. Preamble fields for a particular data storage track on the storage disk are written over multiple revolutions of the storage disk to eliminate low-frequency variations of the preamble stitch line from an ideal position of the preamble stitch line.

Abstract: A hard disk drive includes a housing including a base member and a cover member, a spindle motor disposed in the housing, a data storage disk disposed on the spindle motor, an actuator disposed in the housing to move a read/write head to a position on the data storage disk, a clock signal providing unit disposed on the data storage disk to provide a clock signal of the data storage disk, a position signal providing unit disposed on the actuator to provide a position signal of the actuator, and first and second windows disposed in the housing to correspond to the clock signal providing unit and the position signal providing unit.

Abstract: A disk drive with patterned-media disks has information recorded in the servo sectors that identifies misplacement of the data islands in the data regions between the servo sectors. This misplacement information is read from the servo sectors prior to writing to correct either or both the radial position of the write head and the timing of the write pulses to the data islands. The misplacement information may include radial deviation of the data tracks, circumferential or along-the-track misplacement of the data islands, or the location of defective data islands.

Abstract: Apparatus, methods, and systems can be employed for calibrating servos, and in some implementations, spiral servos are calibrated for use in self-servo-write (SSW) processes. In an aspect, an apparatus includes a timing reference detector configured to determine timing reference information from a back electromotive force signal associated with a rotating machine readable medium, and a servo track window period generator configured to determine a relative location of a spiral on the rotating machine readable medium based on the timing reference information.