Abstract: A magnetic recording and reproduction apparatus, includes a circuit for changing a reference amplitude value of a Viterbi detector. The circuit is used to record and reproduce data with the reference amplitude value displaced from a reference value, thereby measuring the data error rate. Displacement of the reference amplitude from a reference value increases the data error rate, and therefore the data error rate can be measured within a short time. A data error rate with the reference amplitude equal to a reference value is estimated from the data error rate measurement, thereby making it possible to evaluate the degree of accuracy of a magnetic recording and reproduction apparatus. The data error rate is measured with the reference amplitude of the Viterbi detector displaced from a reference value while changing the equalization coefficient value of a waveform equalizer, the cut-off frequency of a low-pass filter and the write precompensation amount of a write precompensation circuit.

Abstract: A magnetic recording head for use in a disc drive system including a rotating disc has a slider body and a transducer on the slider body for reading and/or writing data from and/or to the disc. A piezoelectric sensor is provided on the slider body and produces a signal representing a level of interference between the slider body and the rotating disc. A method of predicting a head crash includes establishing a nominal level of interference between the magnetic recording head and the rotating disc and establishing a threshold interference level difference. The level of interference between the magnetic recording head and the rotating disc represented by the signal provided by the piezoelectric sensor is monitored during operation of the disc drive system. A predicted head crash is indicated when the level of interference between the magnetic recording head and the rotating disc is different from the nominal level of interference by more than the threshold.

Abstract: A method for generating a response in a transconductance circuit includes receiving a circuit differential voltage input and providing a differential voltage input to each of a plurality of differential pairs to control, in part, a differential current generated by each differential pair. Each differential voltage input has a different common-mode voltage level. The method also includes sinking current through each of the differential pairs to control the differential current generated by each differential pair. The magnitude of the current sunk through one of the differential pairs is different from the magnitude of the current sunk through at least one of the other differential pairs. The method also includes combining the generated differential current from each of the plurality of differential pairs to produce a differential current output.

Abstract: On an FCP board and in a head amplifier circuit, provided for amplifying a read signal from a head and supplying the read signal to a read channel, a dummy wiring pattern is located near a wiring pattern for supplying the read signal. The head amplifier circuit incorporates a differential amplifier. The differential amplifier finds and amplifies a difference between the read signal supplied through the wiring pattern and the noise signal supplied through the dummy wiring pattern. The differential amplifier outputs to a read channel the read signal from which the noise has been removed.

Abstract: A method and apparatus for write precompensation in a direct access storage device are provided. A data write encoder generates a data signal to be written. A write precompensation delay circuit is coupled to the data encoder for receiving and delaying the data signal. The write precompensation delay circuit includes a first delay path and a second delay path in parallel with the first delay path. The first delay path and the second delay path have different delay values. In one arrangement, both the first delay path and the second delay path include a plurality of delay cells connected together in a chain. The delay cells of the first delay path have a first predetermined delay value and the delay cells of the second delay path have a second predetermined delay value. A ratio of the second predetermined delay value to the first predetermined value is set equal to one of approximately 3/2, 4/3, 5/4, 6/5, or 7/6.

Abstract: An apparatus and method for recovering from read errors detected by a read channel (70) in a sequence of data read from a disc (18) of a disc drive (10) by using read channel quality indicators to determine the appropriateness of using error correction in combination with other corrective actions utilized in the recovery process. Upon the detection of an uncorrected error in the retrieved data, the disc drive (10) enters a read error recovery routine wherein one or more corrective actions (102, 122) are applied in an effort to resolve the error. One of the channel quality indicators comprises a channel quality measurement (108, 128) determined as the sum of the square of the sampled data bit error values recovered during the read operation.

Abstract: A method and system for resolving error or erasure in binary data streams read back using MR heads from a cyclic, multitracked recording medium. The method assesses whether an erasure or error was coincident with a thermal asperity. If the coincidence occurred, the method branches to and executes an ordered list of data recovery procedures tuned to thermal asperity. This list emphasizes early use of burst ECC correction and alteration of MR head and read channel attributes.

Abstract: A method formats disc surfaces in a disc drive for storage of data in a group of tracks on the disc surfaces. The disc drive performs seek operations to seek among cylinders on the disc surfaces as a function of time according to an actual seek profile. An approximation of the actual seek profile is determined such that the actual seek profile falls within the approximation. The disc surfaces are formatted according to the approximation of the actual seek profile.

Abstract: A thermal asperity-tolerant read channel is provided for a magnetic disk drive. Thermal asperities are detected by a digital detector which includes a pre-filter, a first threshold comparator and, optionally, a second threshold comparator. The pre-filter reduces noise and signal variation in the analog-to-digital converter output to enable better detection of a DC shift caused by a thermal asperity. The first threshold comparator compares the pre-filter output to a predetermined level; if the predetermined level is exceeded, the comparator output is set to one state, providing an initial indication of the presence of a thermal asperity. The optional second threshold comparator determines whether, out of a predetermined number of comparator outputs, the number in the one state exceeds programmed value; if so, the second threshold comparator outputs a final indication of the presence of a thermal asperity.

Abstract: A characteristic of helical scan tracks is that a distortion that occurs in the written data tracks is not uniform over the entire length of the track. Therefore, segments of the helical scan track can be read even though the entirety of the helical scan track cannot be read in a single pass. Therefore, laterally moving the read heads a predetermined distance in a selected direction to access a section of the helical track can produce full amplitude read signals and thereby that section of helical scan track can be read. Once a section of the helical scan track is read, the read heads are moved another incremental distance to access a next section of the distorted helical scan track. Each section of the track is thereby read on a different helical scan as the read heads are incrementally repositioned on each scan. The read sections of the helical scan track are stored in the memory of the tape drive control unit and then used to reconstruct the entirety of the track.

Abstract: In a disk drive which has a magneto-resistance (MR) element as a read element and where servo areas and data areas are separated and recorded on a disk, the disk drive is so constructed as to prevent a read error resulting from the roughness of the disk, i.e, a read error of a thermal asperity. There is provided a structure where, in a servo area, a read error of a start bit of a Gray code is prevented by a thermal asperity which occurs immediately before the Gray code, and where an erase area is detected.

Abstract: A device for formatting a linear data storage tape includes a servo write head configured to write a pattern of magnetic transition stripes along a servo band of the linear data storage tape. The servo write head is configured to produce stripes having lateral widths that are significantly greater than that of a servo read element of a data read/write head designed for use with the linear data storage tape. Each stripe has either a positive non-zero azimuth or a negative non-zero azimuth. The device also includes a magnetic readback element that produces a servo verify signal. The magnetic readback element extends laterally across the full widths of the magnetic transition stripes and is oriented at an azimuth between the positive and negative non-zero azimuths of the magnetic transition stripes. A pulse detector is configured to detect pulses in the servo verify signal.

Abstract: A tape deck system uses four sensors to read features on a tape cartridge to determine control operations. A first sensor determines and a second sensor indicate a condition from a set comprising standard tape cartridge present with file protect, standard tape cartridge present without file protect, cleaning cartridge present, and a standard cartridge quiescent state. The remaining two sensors are used with a special cartridge. The special cartridge has features that indicate, to the first two sensors, that the tape deck system is in the standard cartridge quiescent state. A third and fourth sensors then read features on the special cartridge indicating cartridge type and file protect status. This system allows special cartridges, such as those that may contain thin tape, to only be accessed by tape deck systems equipped to handle the special cartridges. The sensor for indicating the special cartridge type may be modified to also indicate that the cartridge is properly seated in the tape deck.

Abstract: A system and method is disclosed in which a circuit is provided to improve the settling performance of synthesizers used in read/write channel applications when the synthesizer is required to switch frequencies by a small percentage quickly. This is useful in read channel applications where the clock recovery is performed using an all-digital PLL. A digital timing recovery scheme is utilized in which one data frequency synthesizer provides both write and read frequencies. The read frequency is set higher than the write frequency to allow for oversampling when reading data from the storage medium. When changing from a write to read frequency or vice-versa the frequency synthesizer rapidly settles to the new frequency. The frequency synthesizer includes a phase locked loop which utilizes a controllable oscillator. The phase locked loop divisors are changed to obtain the desired frequency changes. An input signal to the controllable oscillator is also changed in order to obtain the rapid settling times.

Abstract: A sub-baud rate write circuit is disclosed which writes RLL encoded channel data to a disk storage medium using a write clock frequency significantly below the baud rate. This allows for a higher channel data rate without increasing the cost and complexity of the write circuitry. The write circuitry operates by re-encoding the RLL encoded channel data according to a particular mapping to generate write data at the write clock rate, and then writing the write data to the disk at appropriate phase delays. The phase delays are generated by passing the write clock through an array of delay circuits. The resulting write signal is the same as if the RLL encoded data were written to the disk using a baud rate write clock. The write circuitry of the present invention is ideally suited for use in a sub-sampled read/write channel where the object is to reduce the cost and complexity by clocking the entire channel at a frequency significantly below the baud rate.

Abstract: A digital VTR is capable of reproducing a recorded picture image in a normal mode and a variable speed reproduction mode. During normal speed reproduction, the digital VTR reproduces a recorded picture from data that has been recorded in a normal play area of a recording medium. When the digital VTR is in a variable low speed reproduction mode, it reproduces a picture from data recorded in a first trick play area. When the digital VTR is in a variable high speed reproduction mode, it reproduces a picture from data recorded in a second trick play area. The first and second trick play areas are located at respective tracks that correspond to different azimuths.

Abstract: A method of managing information to be stored on a storage disc in a disc drive system to achieve improved system performance. In one embodiment, data is preferentially stored on the outer tracks of the disc because system performance is greater when accessing outer tracks. Compression techniques may be employed with this embodiment to limit reductions in the storage capacity of the disc. The compression ratio can have any value, including compression ratios less than 2:1, or of F:1, wherein F is a non-integer. In another embodiment, a storage system is provided having sectors of different sizes. The different sized sectors may be on the same disc surface, on different disc surfaces, or on different disc drives. The differently sized sectors can be used to store blocks of information having different sizes to minimize the number of sectors read, thereby improving system performance.

Abstract: A defect management system for use in a data storage system. The defect management system generates a track defect list comprising a sector defect record for each of a set of defective sectors in a track of a media surface. A sector defect record includes defect management information for each of the defective sectors. The defect management information may be generated according to one of several defect management schemes. The apparatus of the present invention stores the track defect list in a buffer or sector headers. The apparatus of the present invention maps a physical sector number to a logical sector number using the track defect list. If the track defect list is stored in sector headers, the present invention may use a ping-pong FIFO for processing the track defect list.

Abstract: A magnetic head drive of the present invention comprises a composite magnetic head structured by integrally combining a write head into a record head and a magnetic disk having a servo area where position information of the composite magnetic head is recorded and a data area where data is recorded, and the servo area includes a positioning data area having head positioning information, and the head has an erased area generated by recording an AC signal having a frequency higher than a burst pattern in an area other than the burst pattern including information of positioning the composite magnetic head of said positioning data area.

Abstract: A power-reduced digital control within a feedback control loop of a sampling data detection channel controls a predetermined operating parameter of the channel in which an analog to digital converter provides digital samples of information in the channel at a predetermined channel clock rate. The digital control comprises a parameter error extraction circuit clocked at the predetermined channel rate which is connected to receive digital samples from the analog to digital converter, and which extracts parameter error values from the digital samples; an averaging circuit for averaging the extracted parameter error values over an integral submultiple of the predetermined channel clock rate; and a parameter error processing circuit which is connected to the parameter error extraction circuit and clocked at the integral submultiple of the predetermined channel rate for generating and putting out digital control values within the feedback control loop for controlling the predetermined operating parameter.