Abstract: Methods, systems, and devices for coding to decrease error rate discrepancy between pages are described. For example, to identify a unit-distance code for operating a memory device, voltage drifts of a set of read voltages after a duration may be identified and each of the read voltages may be mapped to one of a set of pages of the memory cell using various possible unit-distance codes. Thus, for each unit-distance code the set of pages may be associated with respective subsets of the set of read voltages. Then, for each unit-distance code a set of average read voltage drifts corresponding to one of the set of pages may be identified. The memory device may be operated using a unit-distance code associated with a smaller range of the set of average read voltage drifts than ranges of sets of average read voltage drifts associated with other unit-distance codes.

Abstract: Methods, systems, and devices for coding for quad-level memory cells having a replacement gate configuration are described. Data may be received for storage in a memory device that includes a memory array with memory cells having a replacement gate configuration. The data may be assigned to a plurality of different types of pages within a memory cell of the memory cells using a unit-distance code. The data may be written to the plurality of pages of the different types within the memory cell based at least in part on assigning the data to the plurality of pages of the different types within the memory cell using the unit-distance code to distribute the pages in a way to avoid inconsistent voltage shifting across the plurality of pages of different types.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A byte wide flaw scan interface is used to identify an characterize flaws in a disk medium. In one embodiment, the associated disk drive (100) includes head electronics (120) associated with a disk drive controller (122) via an NRZ interface (127). The NRZ interface (127) 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.