Abstract: This application includes systems and techniques relating to storage devices, such as a device including: a first read channel to process a first input signal obtained from a storage medium using a first read head; a second read channel to process a second input signal obtained from the storage medium using a second read head, which is offset from the first read head in each of two dimensions; a single digital timing loop configured to control interpolation of timing of sampling for first and second analog to digital converters in the first and second read channels; and a two dimensional equalizer coupled with output lines of the first and second read channels; the device being configured to account for a fractional timing difference between the first input signal and the second input signal, the fractional timing difference being a fractional amount of a single clock cycle of the device.

Abstract: The present disclosure describes systems and techniques relating to storage devices, such as storage devices that employ Two Dimensional Magnetic Recording (TDMR). According to an aspect of the described systems and techniques, a device includes: a first read channel to process a first input signal obtained from a Two Dimensional Magnetic Recording (TDMR) storage medium using a first read head, wherein the first read channel includes a first analog to digital converter (ADC); a second read channel to process a second input signal obtained from the TDMR, storage medium using a second read head, wherein the second read channel includes a second ADC; and a single digital timing loop (DTL) for both the first read channel and the second read channel, wherein the single DTL is configured to control interpolation of timing of sampling for the first and second ADCs.

Abstract: A system including an inter-track interference detection module and a position error signal generation module. The inter-track interference detection module determines a first inter-track interference value based on a first signal from a first sensor positioned over a first track of a rotating storage medium. The first inter-track interference value indicates energy contributed by tracks adjacent to the first track compared to energy contributed by the first track. The inter-track interference detection module determines a second inter-track interference value based on a second signal from a second sensor positioned over a second track of the rotating storage medium. The second inter-track interference value indicates energy contributed by tracks adjacent to the second track compared to energy contributed by the second track. The position error signal generation module generates a position error signal based on the first inter-track interference value and the second inter-track interference value.

Abstract: Aspects of the disclosure provide a method for error correction. The method includes error-correction code (ECC) decoding a first code word of code words in a data block, determining erasures for a second code word of the code words in the data block based on corrections in the first code word by the ECC decoding, and ECC decoding the second code word with the erasures.

Abstract: Devices, methods, and other embodiments associated with adjusting a defect threshold are described. In one embodiment, a method includes determining, using a defect threshold, when a read channel has read data from a defective portion of a storage medium. The defect threshold is adjusted based, at least in part, on a gain value and a delayed gain value of a gain loop of the read channel.

Abstract: A system including an inter-track interference detection module and a position error signal generation module. The inter-track interference detection module determines a first inter-track interference value based on a first signal from a first sensor positioned over a first track of a rotating storage medium. The first inter-track interference value indicates energy contributed by tracks adjacent to the first track compared to energy contributed by the first track. The inter-track interference detection module determines a second inter-track interference value based on a second signal from a second sensor positioned over a second track of the rotating storage medium. The second inter-track interference value indicates energy contributed by tracks adjacent to the second track compared to energy contributed by the second track. The position error signal generation module generates a position error signal based on the first inter-track interference value and the second inter-track interference value.

Abstract: The present disclosure describes systems and techniques relating to storage devices, such as storage devices that employ Two Dimensional Magnetic Recording (TDMR). According to an aspect of the described systems and techniques, a device includes: a first read channel to process a first input signal obtained from a Two Dimensional Magnetic Recording (TDMR) storage medium using a first read head, wherein the first read channel includes a first analog to digital converter (ADC); a second read channel to process a second input signal obtained from the TDMR, storage medium using a second read head, wherein the second read channel includes a second ADC; and a single digital timing loop (DTL) for both the first read channel and the second read channel, wherein the single DTL is configured to control interpolation of timing of sampling for the first and second ADCs.

Abstract: Aspects of the disclosure provide a circuit that includes a decoder, an error checking module, and a controller. The decoder is configured to receive codewords, and decode the codewords based on an error correcting code. The error checking module is configured to error-check sectors using an error detecting code in the sectors. Each sector is formed of a plurality of decoded codewords. The controller is configured to store in a memory, when the error checking fails for at least one sector, the decoded codewords and corresponding flags indicative of pass or fail of the decoding of the codewords.

Abstract: A decoder including a decode module, a matrix module, and a marking module. The decode module receives data and performs a first decoding iteration to decode the data. The first decoding iteration includes generating a first matrix having a first byte. The matrix module generates a second matrix based on the first matrix. The second matrix includes the first and second bytes. The second byte is adjacent and sequentially prior or subsequent to the first byte. The marking module: determines whether the first byte has been correctly decoded; based on determining whether the first byte has been correctly decoded, determines a status of the second byte; and based on the status of the second byte, marks the first byte as an erasure. The decode module, based on the second byte being marked as an erasure, corrects the second byte during the second decoding iteration.

Abstract: A method includes: writing data in a magnetic recording system using a write channel of the magnetic recording system; processing output data of the write channel in accordance with a read channel of the magnetic recording system to measure baseline wander; and triggering re-writing through the write channel using different data scramblings when the measured baseline wander fails to satisfy a criterion. The processing can include modeling the read channel of the magnetic recording system, modeling one or more high pass filtering circuits of the magnetic recording system, or both. The writing can include encoding the data after scrambling of the data, the processing can include using a discrete time model of DC offset in the magnetic recording system, and the triggering can include triggering re-writing through the write channel using different scrambling seeds when the measured baseline wander fails to exceed a threshold.

Abstract: The present disclosure describes techniques for DVD-RAM header or land/groove detection. In some aspects, a wobble signal is integrated, an offset is removed from the integrated wobble signal, and a header is detected in the non-offset integrated wobble signal. In some aspects, a threshold value is adjusted based on a comparison of the received wobble signal and the threshold value, and a header is detected based on the adjusted threshold value.

Abstract: A method of operating or calibrating a storage device having a storage medium platter includes writing servo data to the storage medium platter, where the servo data include, for each track on the storage medium platter, a servo sync mark, and a repeating pattern. For each pair of adjacent tracks on the storage medium platter, the repeating patterns, which may be orthogonal, are compared to determine relative phase of the repeating patterns on adjacent tracks. The relative phase for each pair of adjacent tracks is recorded. In another calibration method, first and second repeating patterns may compared to determine whether relative phase of the first and second repeating patterns exceeds a threshold, in which case the second servo data are erased, new second servo data are written, and the comparing and erasing are repeated until the relative phase of the first and second repeating patterns is less than the threshold.

Abstract: A hard disk drive circuit includes first and second inter-track interference detection modules. The first inter-track interference detection module is configured to generate a first measured inter-track interference value based on a first read signal from a first read sensor positioned over a magnetic medium. The second inter-track interference detection module is configured to generate a second measured inter-track interference value based on a second read signal from a second read sensor positioned over the magnetic medium. A position error signal generation module is configured to generate a position error signal based on the first measured inter-track interference value and the second measured inter-track interference value. An arm control module is configured to control rotation of an arm in response to the position error signal. The first read sensor and the second read sensor are located at a distal end of the arm.

Abstract: A plurality of time periods corresponding to times at which a predicted transition in a signal is expected to occur are determined. The signal has bi-phase modulation, and the predicted transition corresponds to a transition in the signal from a first state to a second state as part of the bi-phase modulation. A next transition in the signal from the first state to the second state is detected, and it is determined whether the detected next transition occurred during one of the plurality of time periods. In response to determining that the detected next transition occurred during one of the plurality of time periods, a timing of the detected next transition is used to adjust a clock used for recovering channel bits in the signal.

Abstract: Determining the radial position of a first read head of a storage device includes reading servo data from a storage media platter surface using the first read head, deriving from that servo data a first positron error signal representing a first estimate of the radial position of the first read head, reading the servo data from the storage media platter surface using a different read head, deriving from that servo data a second position error signal representing an estimate of the radial position of the different read head, and combining the first estimate of the radial position of the first read head and the estimate of the radial position of the different read head to obtain a revised estimate of the radial position of the first read head. The combining could include taking account of a known positional offset between the first read head and the different read head.

Abstract: Systems and methods for detecting cycle slip are provided. In some embodiments, a waveform that represents data samples is received. The waveform may include a predetermined preamble and a predetermined postamble. A first value representing a phase of the predetermined preamble of the waveform may be computed. A second value representing a phase of the predetermined postamble of the waveform may be computed. A detection is made as to whether cycle slip occurred during sampling the received waveform based on a comparison of the first value with the second value.

Abstract: Aspects of the disclosure provide a circuit that includes a decoder, an error checking module, and a controller. The decoder is configured to receive codewords, and decode the codewords based on an error correcting code. The error checking module is configured to error-check sectors using an error detecting code in the sectors. Each sector is formed of a plurality of decoded codewords. The controller is configured to store in a memory, when the error checking fails for at least one sector, the decoded codewords and corresponding flags indicative of pass or fail of the decoding of the codewords.

Abstract: Aspects of the disclosure provide a sync mark detector. The sync mark detector includes a first unit configured to decay over time a value indicating a length of a bit format, a second unit configured to compare the decayed value with a detected length of the bit format to determine a new length, and a third unit configured to detect a sync mark based on the detected length and the new length.

Abstract: Aspects of the disclosure provide a signal processing circuit that has fast response time to sudden profile changes in an electrical signal. The signal processing circuit includes a processing path configured to process an electrical signal that is generated in response to reading data on a storage medium, and a feed-forward correction module. The feed-forward correction module is configured to detect a profile variation based the electrical signal in a time window, and correct the electrical signal in the time window based on the detected profile variation.

Abstract: A hard disk drive circuit includes first and second inter-track interference detection modules. The first inter-track interference detection module is configured to generate a first measured inter-track interference value based on a first read signal from a first read sensor positioned over a magnetic medium. The second inter-track interference detection module is configured to generate a second measured inter-track interference value based on a second read signal from a second read sensor positioned over the magnetic medium. A position error signal generation module is configured to generate a position error signal based on the first measured inter-track interference value and the second measured inter-track interference value. An arm control module is configured to control rotation of an arm in response to the position error signal. The first read sensor and the second read sensor are located at a distal end of the arm.