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, wherein the servo tracks form a plurality of servo zones, and a servo data rate of servo sectors in a first servo zone is different than a servo data rate of servo sectors in a second servo zone. A disk locked clock is synchronized to the data rate of the servo sectors in the first servo zone, wherein the disk locked clock for generating a timing window relative to the servo sectors. When the head crosses from the first servo zone to the second servo zone, at least one of the disk locked clock and the timing window is adjusted to compensate for a timing transient.

Abstract: A system and method of establishing write timing in a disk drive using bit patterned media and a magnetic head with read-write offset in which servoing and writing occur on different tracks with timing offsets. Initially, the distance between the servoing and writing tracks is determined for each track/head position in accordance with head geometry and skew angle. The relative timing errors are then measured by iteratively writing data at timing offset increments to determine the optimal timing offset for the servoing/writing track pair, and then writing the offset to sync fields on the servoing tracks of the disk.

Abstract: An apparatus comprises read channel circuitry and associated signal processing circuitry comprising frontend processing circuitry and backend processing circuitry. The frontend processing circuitry comprises a loop detector and equalizer configured to determine an equalized read channel signal from a read channel signal and a decoding module configured to apply verification and scrambling processing on a decoded read channel signal. The backend processing circuitry comprises a backend detector, an interleaver, a backend decoder, and a de-interleaver configured to perform an iterative decoding process on the equalized read channel signal to determine the decoded read channel signal. The frontend processing circuitry is controlled by a first clock having an associated first clock rate and the backend processing circuitry is controlled by a selected one of the first clock and a second clock having an associated second clock rate determined at least in part by the first clock rate and a maximum clock rate.

Abstract: A method for recording data to a magnetic media while simultaneously reading sync and or servo data with reduced noise from the write head affecting the reading of the sync and or servo data. The invention records data using a write head of a first slider and reads the sync and or servo data from a read head located on a different slider that is facing a different disk surface than the first slider. In this way, magnetic or thermal noise from the write head does not affect the reading of the sync and or servo data.

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: Methods and apparatus are provided for detecting a sync mark in a storage system, such as a hard disk drive. A sync mark is detected in a storage system by obtaining one or more branch metrics from a data detector in the storage system; generating one or more sync mark metrics using the one or more branch metrics from the data detector; and identifying the sync mark based on the sync mark metrics. An input data set is optionally compared with a plurality of portions of a sync mark pattern to yield corresponding comparison values and the comparison values can be summed to obtain at least one result. A sync mark found signal is asserted based upon the at least one result.

Abstract: A disk drive is described with a single servo master timer that is used to control timing critical signals such as servo gate, SAM windows, channel power save, PREAMP power save and so on. The master timer is adjusted to compensate for SAM detection errors (early, late or missed) and provides improved servo timing quality. In an embodiment the adjustable master timer can be selectably clocked by either the DLC/DSW clock or the system clock.

Abstract: Synchronization technologies for disk drives are described. A described technique includes receiving a waveform produced by a read head operated with respect to a recording medium including magnetic data positions, a first servo sync mark (SSM), a second SSM, and phase tracking fields (PTFs); producing, based on the waveform, a servo detect pulse that indicates a detection of at least one of the SSMs; controlling a first adjustment of a phase of a write clock signal, the first adjustment being responsive to the servo detect pulse; producing, based on the write clock signal, samples of the waveform that correspond to the PTFs; and controlling second adjustments of the phase based on the samples to align the write clock signal with at least a portion of the data positions, the second adjustments being responsive to the PTFs, respectively.

Abstract: A system and method for recording data to a perpendicular magnetic recording media having a highly ordered granular structure. The method includes the synchronization of write frequency and write phase to the granular structure of the magnetic media optimize performance of the magnetic data recording system by minimizing bit error rate.

Abstract: Synchronization technologies for disk drives are described. A described technique includes producing signals that include processing a waveform produced by a read head operated with respect to a recording medium including magnetic data positions arranged on tracks including first and second tracks; producing, based on the waveform, a servo detect pulse that indicates a detection of servo data on the first track; measuring a timing difference that is based on the servo detect pulse and a write pulse of a write clock signal; 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 data positions; and controlling a write head to write to one or more data positions of the second track based on the write clock signal while a servo clock signal is servo locked on the first track.

Abstract: A system including a storage device, a channel module, a sampling module, a first phase module, and an adjustment module. The storage device includes servo sectors, and discontinuous media with bit islands. The channel module reads the servo sectors based on a servo clock to generate an analog signal. The sampling module samples the analog signal based on a servo clock signal to generate first samples, and based on a write clock signal to generate second samples. The first phase module estimates a phase of the write clock signal based on the first samples, and the second samples. The adjustment module adjusts the phase of the write clock signal based on the estimated phase of the write clock signal. The channel module, based on the write clock signal with the adjusted phase, writes data to the bit islands of the discontinuous media.

Abstract: Various embodiments of the present invention provide systems and methods for data processing. As an example, a data processing circuit is disclosed that includes an equalizer circuit and a data detection circuit. The equalizer circuit is operable to filter a series of samples based at least in part on a filter coefficient and to provide a corresponding series of filtered samples. The data detection circuit includes: a core data detector circuit and a coefficient determination circuit. The core data detector circuit is operable to perform a data detection process on the series of filtered samples and to provide a most likely path and a next most likely path. The coefficient determination circuit operable to update the filter coefficient based at least in part on the most likely path and the next most likely path.

Abstract: A disk drive is described with a single servo master timer that is used to control timing critical signals such as servo gate, SAM windows, channel power save, PREAMP power save and so on. The master timer is adjusted to compensate for SAM detection errors (early, late or missed) and provides improved servo timing quality. In an embodiment the adjustable master timer can be selectably clocked by either the DLC/DSW clock or the system clock.

Abstract: Embodiments described herein provide for robust servo patterns that comply with planarization constraints and also allow use of a single master template for manufacture of both the front and back of a magnetic disk. Planarization constraints are met because only a portion of servo data is hard patterned on the magnetic disk and the hard patterned servo data areas comply with planarization constraints. The servo pattern has two symmetrical servo write assist patterns, one on each side of a central burst pattern. The servo sync, SAM, track-ID, sector-ID, and/or RRO values can be written magnetically by the write head onto these servo write assist patterns after the completion of the planarization process. The symmetric design of the servo pattern allows both a left-to-right and a right-to-left servo write and read back, thereby enabling use of a single master template in magnetic disk manufacture.

Abstract: Described embodiments provide an interleaved sampler having N sample and hold circuits for sampling an input signal, and M multiplexers. Each multiplexer is adapted to couple all N of the plurality of sample and hold circuits to a respective output of the interleaved sampler. The interleaved sampler samples at a sample rate of fs, has an interleaved sampling period of M/fs, where M is greater than one and less than N. Because there are more sample and hold circuits than there are samples taken during an interleaved sampling period, different combinations of the sample and hold circuits are used from interleaved sample period to interleaved sample period. This reduces spurious tones generated from offset voltages when using interleaved sample and hold circuits. The order of the sample and hold circuits are clocked might be random, pseudorandom, or a fixed pattern longer than the interleaved sampling period.

Abstract: A magnetic recording disk drive determines the locations of defective bits in a failed data sector, and allows for the error correction code (ECC) to correctly decode the data from the sector. After a sector has failed decoding, the digitized waveform and the read channel state from the failed sector are stored in memory. A nondata pattern is written to the failed sector and read back to determine the locations of the defective data bits in the failed sector, which are then used to update the read channel state. The data pattern from the failed sector, with the identified bit error locations, is attempted to be decoded. If the decoding is successful then the sector is marked as bad and the correctly decoded data pattern is written to a different region of the disk, for example physical sectors specifically intended for use as spare sectors.

Abstract: A bit patterned recording system includes a servo channel module configured to recover servo fields written with servo information. A field locator module is configured to locate a field printed to data islands of a medium based on a location of one of the servo fields. The servo islands and the data islands have different spacing. A servo clock has a different phase and frequency than a data clock. A phase error calculator module is configured to estimate a phase error of the data clock based on the field and the data clock. The phase error is used to adjust a phase of the data clock.

Abstract: A hard disk drive or other storage device comprises a storage medium, a read head configured to read data from the storage medium, and control circuitry coupled to the read head and configured to process data received from the read head. The control circuitry comprises read channel circuitry that includes a low-density parity check decoder or other type of decoder. Power management circuitry associated with the read channel circuitry is configured to detect a power control condition of the read channel circuitry and to control insertion of idle clock cycles in a clock signal supplied to the decoder responsive to the detected power control condition. For example, the read channel circuitry may comprise a clock generator configured to gate the clock signal responsive to a control signal from the power management circuitry.

Abstract: A given reference pattern is written on bit patterned media that has an initial reference pattern already disposed thereon. A write phase and frequency is detected based on the initial reference pattern and the given reference pattern is written on the bit patterned media at the detected write phase and frequency.

Abstract: A disk drive is disclosed comprising a head actuated over a disk, the disk comprising a plurality of servo sectors defining a plurality of servo tracks, wherein the servo tracks form a plurality of servo zones. A servo data rate of servo sectors in a first servo zone is different than a servo data rate of servo sectors in a second servo zone. A boundary of a first servo zone overlaps with a boundary of a second servo zone over a transition zone. The servo sectors of the first servo zone are interleaved with the servo sectors of the second servo zone within the transition zone. At least one servo parameter is adjusted when the head is over the transition zone in order to transition between the first servo zone and the second servo zone.

Abstract: The present disclosure describes systems and methods for controlling synchronization of a servo clock by tying the triggering of the gate signal of the position error signal field of the short servo wedge portion directly to the synchronization marker in the full servo wedge. The systems and methods described herein include controlling synchronization of a servo clock for reading servo information from a disk that is rotating relative to a read head. The systems and methods may include estimating a gate delay corresponding to a position error signal (PES) field in a short null servo wedge based, at least in part, on the location of the servo synchronization marker. The systems and methods include producing a servo clock timing control signal based on the estimated gate delay, and applying the servo clock timing control signal to the servo clock.

Abstract: A disk drive is disclosed comprising a disk comprising a plurality of servo tracks defined by servo sectors. The disk drive further comprises a head comprising a read element offset linearly from a write element by a gap such that when the disk rotates, the read element reaches a servo sector before the write element. During a first operation, a first length of a beginning of the servo sector is read, and during a write operation, a second length of the beginning of the servo sector shorter than the first length is read to enable data to be written while the read element is over at least part of the servo sector.

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: A system includes a management module transferring sectors between an interface or a memory and ports. The management module transfers a first portion of a first sector to or from a first port while transferring to or from a second port a second portion of the first sector or a first portion of a second sector. A first channel module reads from or writes to a first surface of a disk via a first head by transferring the first portion of the first sector to or from a first amplifier module. A second channel module, while the first channel module transfers the first portion of the first sector to or from the first amplifier module, reads from or writes to a second surface of the disk via a second head by transferring to or from a second amplifier module the second portion or the first portion of the second sector.

Abstract: A read channel is configured to receive at least part of a data fragment read from a storage media into a register, wherein the data fragment is configured to be formatted with a preamble, a sync mark (e.g., a syncMark), and user data, and wherein the data fragment is missing a sync mark. A position in the data fragment is selected, a sync mark is assumed at the selected position. The data is then processed assuming the sync mark is at the selected position of the data fragment to determine whether the data converges. When a determination is made that the data converges, the data is recovered.

Abstract: A read channel is configured to receive at least part of a data fragment read from a storage media into a register, wherein the data fragment is configured to be formatted with a preamble, a sync mark (e.g., a syncMark), and user data, and wherein the data fragment is missing a sync mark. A position in the data fragment is selected, a sync mark is assumed at the selected position. The data is then processed assuming the sync mark is at the selected position of the data fragment to determine whether the data converges. When a determination is made that the data converges, the data is recovered.

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 or otherwise associated with the read/write head. The control circuitry comprises a write driver configured to generate a write signal for data to be written to the storage disk, and a multiple-slope transition controller associated with the write driver and configured to control a data transition in the write signal such that the data transition comprises at least two different segments each having a different slope, with the transition controller comprising separate slope control mechanisms for each of the segments. By way of example, the data transition may comprise a dual-slope transition having first and second segments arranged sequentially between a start point and an end point of the data transition.

Abstract: A clock phase measurement circuit comprises a selector circuit operable to inject one of a first analog clock signal or a second analog clock signal into a signal path configured to carry an analog data signal, so that the injected analog clock signal replaces the data signal. An Analog to Digital Converter (ADC) converts the injected analog clock signal to a digital clock signal. A counter selects a time, using the second analog clock signal, to determine at least one of a phase or a magnitude of the digital clock signal. A measurement circuit determines at least one of the phase or the magnitude of the digital clock signal for at least one frequency at the selected time.

Abstract: A system includes a self-servo-write (SSW) module, a read module, and a write module. The SSW module writes servo spirals on a magnetic medium of a hard disk drive (HDD) via a write head of the HDD. The read module reads the servo spirals via a read head of the HDD and generates read signals. The write module writes non-servo data on the magnetic medium via the write head based on the read signals before the SSW module writes servo wedges on the magnetic medium.

Abstract: According to an aspect of the present disclosure, a method includes: receiving a plurality of groups of one or more phase signals, each group of phase signals having a different phase relative to other groups of one or more phase signals; generating a plurality of interpolated phase shifted signals based on the plurality of groups of one or more phase signals, wherein the plurality of interpolated phase shifted signals do not have an associated common mode component; receiving data bits and precompensating each data bit in accordance with a given interpolated phase shifted signal; and selecting a precompensated data bit for output.

Abstract: Techniques are provided for performing bit-locked operations on media. A first control signal is received from a first source, and a second control signal is generated at a second source in response to receiving the first control signal. The media is accessed according to the second control signal. One or more synchronization markers are located during the accessing of the media, and bit-level synchronization between the second source and the media is achieved based, at least partially, on the one or more synchronization markers. A control operation is performed on the media with bit-level synchrony between the second source and the media.

Abstract: A write clock synchronization system includes a first module configured to generate a write clock signal. A second module is configured to, based on a sensor signal received, detect a pattern of bit islands on bit-patterned media. The second module is configured to determine a phase error of the write clock signal based on the pattern of the bit islands. A third module is configured to at least one of adjust or select a phase of the write clock signal based on the phase error.

Abstract: In one aspect, systems, apparatuses and techniques obtain, through read circuitry, timing information for a machine-readable medium to determine head position; and write, by write circuitry, a first set of spiral servo reference tracks at a first frequency on a first zone of the medium and a second set of spiral servo reference tracks at a second, different frequency on a second zone of the medium. The second zone may be different from the first zone. Further, at least one of the first and second sets of spiral servo reference tracks may be written to the medium based on at least the timing information.

Abstract: Methods, systems, and apparatus, including computer program products, are described for calibrating servos, and in some implementations for calibrating spiral servos for use in self servo write processes. In one aspect, a method is provided that includes measuring a slope of a spiral written to a machine readable medium, and adjusting a parameter in accordance with the measured slope to calibrate spacing of servo tracks, with respect to variation between a target slope and the measured slope for the spiral, for writing the servo tracks to the machine readable medium using the spiral as a reference and the adjusted parameter to generate a same radial spacing between servo tracks from spirals with different slopes.

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 a data stream processor operable to generate a number of data streams at different frequencies based on an input data stream, a number of servo preamble detectors each operable to process a different one of the data streams to detect a servo preamble, a selector operable to output one of the data streams in which the servo preamble was detected as a winning data stream, and a pattern detector operable to detect a pattern in the winning data stream.

Abstract: In a magnetic recording device adopting a microwave assisted recording method, a microwave frequency on a positive polarity side and a microwave frequency on a negative polarity side are adjusted to be optimal. The magnetic recording device of the invention supplies to a magnetic head a write current of which a current waveform on the positive polarity side and a current waveform on the negative polarity side are asymmetric.

Abstract: A method for reducing a disturbance associated with repeatable runout associated with a removable disc loaded into a storage system. The method includes, at the storage system: logically partitioning the removable disc into sectors; for each of the sectors, obtaining a corresponding profile of repeatable runout contained in the sector; and applying a runout control algorithm to each of the sectors to generate a repeatable runout control (RROC) waveform that is usable to suppress the repeatable runout in the sector as indicated by the profile corresponding to the sector. The method also includes, at the storage system: assembling each RROC waveform to generate a single RROC waveform that is useable to suppress repeatable runout as contained in an entire revolution of the removable disc; and storing, in a memory, the single RROC waveform.

Abstract: A transmission apparatus stores frame data of a first frame in a second frame having a bit rate different from that of the first frame through regulation of the amount of stuffs to be stored in the second frame. The transmission apparatus includes: a storage unit storing the first-frame frame data; a first control unit controlling a timing of writing the first-frame frame data in the storage unit based on first stuff information indicating the amount of stuffs contained in the first frame; an arithmetic and logic unit obtaining second stuff information indicating the amount of stuffs to be contained in the second frame based on a bit rate ratio between the first frame and the second frame; and a second control unit controlling a timing of reading out the first-frame frame data stored in the storage unit based on the second stuff information.

Abstract: An initial phase offset between a center track and a side track is determined. An initial side track pulse shape is determined using the initial phase offset and side track interference. The initial side track pulse shape minimizes a contribution of the side track interference to a center track bit. The contribution of the side track interference is removed from the center track bit using the initial side track pulse shape and the side track interference.

Abstract: User level data associated with a location adjacent to a desired location on a magnetic disk storage is received. Media level data associated with the adjacent location is generated based at least in part on the user level data associated with the adjacent location; a processor which is configured to generate the media level data associated with the adjacent location is a same processor which is configured to generate media level data based at least in part on user level data during a write process. The media level data associated with the adjacent location is used to remove inter-track interference (ITI) associated with the adjacent location from a signal read back from the desired location.

Abstract: Described embodiments provide an interleaved sampler having N sample and hold circuits for sampling an input signal, and M multiplexers. Each multiplexer is adapted to couple all N of the plurality of sample and hold circuits to a respective output of the interleaved sampler. The interleaved sampler samples at a sample rate of fs, has an interleaved sampling period of M/fs, where M is greater than one and less than N. Because there are more sample and hold circuits than there are samples taken during an interleaved sampling period, different combinations of the sample and hold circuits are used from interleaved sample period to interleaved sample period. This reduces spurious tones generated from offset voltages when using interleaved sample and hold circuits. The order of the sample and hold circuits are clocked might be random, pseudorandom, or a fixed pattern longer than the interleaved sampling period.

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 waveform produced by a head operated with respect to a magnetic rotating recording medium; operating a model-based predictor based on model parameters to produce one or more model-based predictor outputs to compensate for deterministic disturbances in an area situated on a portion of a track on the recording medium; operating a stochastic predictor based on the timing data to produce one or more stochastic predictor outputs to compensate for nondeterministic disturbances in the area; and performing one or more clock frequency adjustments that are responsive to the head being operated within the area, the one or more clock frequency adjustments being based on the one or more model-based predictor outputs and the one or more stochastic predictor outputs.

Abstract: An apparatus according to one embodiment includes a digital correlator configured to compute a correlation signal between a sequence of samples of a readback servo signal and a reference waveform. A timing reference module is configured to provide a reference timing model comprising one or more interpolation instants to the digital correlator, wherein the correlation signal determined at each interpolation instant yields a detection metric for one data symbol. A correlation interpolator is configured to interpolate the correlation signal at the interpolation instants and compute a longitudinal position (LPOS) detection metric according to the interpolated correlation signal samples.

Abstract: A method for reading a current track of data from a storage device includes using a first read head to read the current track of data and at least a first portion of at least one adjacent track of data, using at least a second read head to read at least a portion of the current track of data and at least a second portion of the at least one adjacent track of data, and decoding the data read from the current track, including processing signals from the first read head and the at least a second read head, to at least partly remove, from the signal from the first read head, contributions from the first portion of the at least one adjacent track of data. The decoding may include deriving expressions relating contributions from the current and adjacent tracks, and solving the expressions using least-mean-square analysis.

Abstract: A method of storing data in a storage medium includes determining a compensation unit for a portion of the storage medium, reading a first set of bit values from the portion of the storage medium, determining a compensation value based at least in part on an erroneous bit value of the first set of bit values and the compensation unit, and storing the compensation value in association with the portion of the storage medium.

Abstract: A disk drive is disclosed comprising a head actuated over a disk, and a spindle motor operable to rotate the disk. A bootstrap spiral track is written to the disk, wherein the bootstrap spiral track comprises a high frequency signal interrupted by sync marks. A first sync mark is written while writing a first part of the bootstrap spiral track, and a second sync mark is written while writing a second part of the bootstrap spiral track. A switch between writing the first sync mark and the second sync mark is made in response to a spindle BEMF voltage, thereby generating a sync mark seam in the bootstrap spiral track.

Abstract: Approaches for determining the timing latency of a communication path are described. Some embodiments involve a method for testing timing latency. A signal is driven on a first data path and is returned through a second data path through a loop back element. The timing latency of at least a portion of the communication path that includes the first data path and the second data path is tested using the signal returned on the second data path. The gain of the second data path is adjusted to a test value during the testing of the timing latency.

Abstract: A patterned-media magnetic recording disk drive has head positioning servo sectors on the disk that do not contain special patterns but merely use the same type of dots that are used for data. The “data” dots in angularly spaced sectors of the data tracks function as the servo sectors and are denoted as D-servo regions. The D-servo regions extend across an annular band of the disk, which may be a bootstrap band for self-servowriting. The dots in the annular band are randomly magnetized so that each track in each D-servo region provides a generally random readback signal at the data frequency. The precise radial and circumferential position of the read/write head within a D-servo region is determined by comparing the readback signal with a set of reference signal waveforms from a look-up reference table and finding the reference signal waveform that matches the readback signal.

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: 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.