Abstract: Apparatus and method for transferring data in a disc drive data handling system. A read/write head having separate write and read elements is used to write data to and transduce data from a disc recording surface. A preamplifier driver circuit applies write currents to the write element to write data to the recording surface and to apply a first read bias signal of selected, nonzero magnitude to the read element to transduce data from the recording surface. In response to the assertion of a write gate signal, the preamplifier driver circuit generates a second read bias signal of selected, nonzero magnitude and applies the second read bias signal to the read element while applying the write currents to the write element. This reduces the potential for damage to the read element due to cross-talk noise induced in the read bias signal from magnetic coupling between the read and write elements.

Abstract: A method and apparatus for detecting and recovering from head instability in a magneto-resistive (MR) transducer head of a disc-drive system. A head-instability-recovery circuit is described for use in disc drive to recover from a head-instability condition of an MR transducer head. This circuit includes a controller and a current source that supplies current to the MR head. The current source is controlled to supply a nominal amount of current to the MR head when operating in a normal mode, and to supply one or more current bursts having a current above the nominal supply current in order to recover from the head-instability condition. Also described is a method for recovering from a transducer-instability condition of an MR transducer of a disc drive, including detecting a situation that indicates a head-instability-recovery operation is desired, and performing the head-instability-recovery operation.

Abstract: A method and apparatus are provided for reading from a storage medium to form data values. A signal is generated from a sector on the storage medium and a section of that signal is identified as having a change in amplitude. A gain multiplier is activated to multiply that section of the signal by a gain value. The gain multiplier is deactivated at the end of the section so that the remaining portion of the sector signal is not multiplied by the gain value. This results in a defect adjusted signal that is applied to a detector to detect data values.

Abstract: A method for monitoring a data storage medium is provided in which a virtual head fly profile is measured. In addition, a data storage device for implementing the monitoring method is provided.

Abstract: A writer coil in a data head of a data storage system is tested by coupling detection circuitry to the writer coil and driving the writer coil with a periodic pulse signal generated by the detection circuitry. As a result, voltage is generated, with the detection circuitry, as a function of an inductance of the writer coil. An inductance of the writer coil is calculated as a function of the generated voltage. Electrical short circuits and discontinuities in the writer coil are identified as a function of the calculated inductance.

Abstract: A method for determining whether a head of a data storage device exhibits head instability. A disc attached to a spindle motor is accelerated to an operating rotational velocity to aerodynamically support the head, the head is positioned over a portion of the disc and a pattern of selected frequency is written. A readback signal is provided to a head instability detection circuit by a magnetoresistive element of the head reading the selected frequency pattern for detection and comparison of an occurrence of randomly repeatable amplitude spikes in relation to predetermined threshold levels.

Abstract: A system and method for performing read retry operations with respect to an erroneously read data sector is disclosed. The system and method use estimates of bit error rates determined during previous attempts to read data from the sector to determine an optimal distance and direction to move a read transducer for a subsequent read retry of the erroneously data sector.

Abstract: An apparatus and associated testing method for identifying void heads in magnetic storage systems in which a first bit error rate is determined using data written at a first overshoot amount. A second bit error rate is determined using data written at a second rate current in a second overshoot amount. A physically damaged transducer head is identified based upon a comparison of the first bit error rate to the second bit error rate.

Abstract: A magnetoresistive element measurement circuit configured for measuring resistance of a magnetoresistive element biased by a current source is disclosed. In a preferred embodiment, the measurement circuit includes the magnetoresistive element, a current source providing a fixed current to the magnetoresistive element, at least one current bypass switch controllingly engaging a measurement resistor in an electrical parallel configuration with the biased magnetoresistive element, and an analogue voltage detector measuring voltage first across the biased magnetoresistive element and then across the biased magnetoresistive element in electrical parallel communication with the measurement resistor. The measured voltages are factored with the measurement resistor to determine the resistance of the magnetoresistive element.

Abstract: Apparatus for detecting defect in a recordable medium such as a disc drive is disclosed. The apparatus includes a recording system which write and read test data on the medium. The apparatus also includes a first comparator for comparing the read data to a first threshold. A first and a second counter, operably connected to the first comparator, are incremented when the read data exceeds the first threshold. When the first counter obtains a first count value, a first defect signal is produced. Data domains associated with the recordable medium are marked as bad in response to the first defect signal. When the second counter obtains a second count value, a second defect signal is produced and data sectors associated with the recordable medium are marked as bad in response to the second defect signal. A method for detecting defects in a recordable medium is also disclosed.

Abstract: A process of run-time temperature compensating bias current to a magnetoresistive read head in which a plurality of temperature ranges are defined with associated bias current values. A hysteresis range of temperatures is defined for each boundary between temperature ranges. A bias current value is selected based on the temperature range of the sensed temperature. The process is repeated. If the sensed temperature is in a different temperature range from that previously identified and the measured temperature is not in a hysteresis range at the boundary with the temperature range previously identified, the selected bias current value is based on the presently identified temperature range. If the sensed temperature is in a hysteresis range at the boundary with the temperature range previously.

Abstract: A method of manufacturing disc drives. Before a pivot cartridge is assembled into a disc drive, impedance readings of the pivot cartridge are taken, preferably, at more than one rotational position and across a frequency range. The pivot cartridge is accepted for assembly into the disc drive only if its impedance readings compare favorably with readings taken of a good pivot cartridge. Otherwise, the pivot cartridge is rejected and the impedance readings are analyzed to provide identification of the defect in the pivot cartridge. In addition, a system and a storage device readable by a computer system for implementing the method of screening pivot cartridges and identifying causes of defects is provided.

Abstract: A method for characterizing a bearing cartridge based on a preload applied to the bearing cartridge used in a disc drive, to increase disc drive yield rates. The method begins by loading the bearing cartridge on to a test fixture and to an actuator assembly such that the actuator is rotatably attached to the base by the bearing cartridge. Then, the method includes inducing a steady swing in the actuator. Then, the method includes measuring a voltage drop that occurs across the bearing cartridge during the steady swing to characterize the preload applied to the bearing cartridge.

Abstract: A method is disclosed for detecting defects in a recordable medium such as a hard disc drive based on error energy. The method may include the steps of writing test data to the medium and reading back the test data. The method may also include the steps of computing an error energy based on the square of the difference between the read back data and an ideal version of the test data and comparing the error energy with an energy threshold. The method generates a defect signal when the error energy exceeds the energy threshold. The method may also be used to identify the media defect according to its error energy profile. An apparatus for detecting defects in a recordable medium is also disclosed.

Abstract: A representation of the signal level on a data head is obtained by combining the signal level values corresponding to more than one sector of a track on a disc surface. This makes it much easier to lock on to a relatively accurate representation of the actual head signal amplitude, even in the presence of servo disturbances.

Abstract: A method for optimizing the read-to-write offset of a disk drive system in respect of a track is provided. In one aspect the method includes the step of determining a first read position amongst a range of test positions offset relative to the track on the basis of read signal strength. The method further includes the steps of calculating a subrange of test positions about the first read position, selecting a second read position from the subrange on the basis of bit error rates and setting the read-to-write offset as a function of the second read position. In addition a disk drive system including means for optimally setting the read-to-write offset in respect of a track is provided.

Abstract: A bias current for a magnetoresistive read head is selected by defining a tuning range based on a maximum and a minimum bias current value for the head. A plurality of read operations are iteratively performed using a different bias current value over the tuning range for each iteration. The results of each read iteration are measured and a bias current is selected on the basis of the read error rates, and particularly those bias currents associated with the lowest read error rate.

Abstract: A guardband portion is written on a disc surface in a disc drive. A predetermined data pattern is written on at least one data track adjacent to the guardband portion. A predetermined guardband pattern is written at a plurality of different guardband frequencies in the guardband portion. For each guardband frequency, at least one performance criterion is measured for the data track. A desired guardband pattern is written on the guardband portion of the disc surface at a guardband frequency chosen based on the measured performance criterion.

Abstract: A disc drive with on-the-fly verification of an enabled condition of the write element, comprising a rotatable disc having a magnetic recording surface, and a data reading and writing assembly. The data reading and writing assembly comprises a read/write head comprising a write element and a read element, both adjacent the recording surface; a preamplifier comprising a write driver applying a series of write currents for writing data to the recording surface and a read amplifier for reading stored data from the recording surface; and an interconnect joining the write driver to the write element so as to generate time-varying magnetic fields selectively magnetizing the recording surface in response to the write currents, and joining the read amplifier to the read element so as to transduce magnetization vectors on the recording surface associated with stored data.

Abstract: Method and apparatus for detecting defects in a magnetic medium of a data handling system. The magnetic medium includes a number of user data wedges each disposed between an adjacent pair of servo data wedges. A predetermined data sequence is written to the user data wedges, and subsequently read to generate a readback signal. A sequence of discrete time sample values are generated from the readback signal. Defects in the medium are detected in relation to the magnitudes of the discrete time samples. A media scan controller outputs a first multi-bit information record having at least one bit composing the address of the user data wedge containing a defect, and a second multi-bit information record having at least one bit composing an address of the defect within the user data wedge. No information is written to the buffer when no defects are identified.