Abstract: In a magnetic disk storage system, a sampled amplitude read channel is disclosed that employs a fault tolerant sync mark detector for detecting a sync mark from the channel samples in order to synchronize a time varying sequence detector. The read channel preferably employs PR4 equalization for timing recovery and gain control, and EEPR4 equalization for sequence detection. The EEPR4 sequence detector operates according to a time varying state machine matched to a predetermined trellis code constraint. Because the state machine is time varying, the data stream must be synchronized at the input of the sequence detector rather than at the output as in the prior art. The present invention provides a fault tolerant sync mark detector that detects a sync mark from the EEPR4 channel samples before being input into the sequence detector.

Abstract: Disclosed is a method for determining an exact address of sectors retrieved from a media that is formatted in a headerless format. The method includes the acts of requesting a desired sector. Associating a seed value to the desired sector. Retrieving an initial sector from the media in response to the requested desired sector. Calculating an error detection and correction over the initial sector and the seed value that is associated with the desired sector to produce a seed error pattern at a seed location. The method further includes, in one embodiment, the act of performing a logical XOR operation between the seed error pattern and the seed value to produce an exact address of the initial sector that is retrieved from the media. Once the exact address of the initial sector is ascertained, a transition may be made to the desired sector. On the other hand, the data beginning at the received sector may be used.

Abstract: A servo sector allocation scheme for a disk based data storage system is disclosed that realizes an increased servo sampling rate without an associated increase in overhead. The scheme involves increasing the number of servo sectors on a subset (preferable one) of the disk surfaces in the disk drive while reducing the number on all remaining disk surfaces. A master servo feedback signal is then derived from the highly populated surface(s) and a slave servo feedback signal is derived from the surface that is being accessed. The master and slave servo feedback signals are then combined to form a single position error signal that is used to control the positioning of an appropriate transducer.

Abstract: A magnetic tape servo pattern including track identification. Information from a track identification area intersecting one or more tracks on each frame in combination with information identifying the track as odd or even, is used to uniquely identify the track.

Abstract: The invention provides a method for effectively removing the cause of a thermal asperity (TA) phenomenon occurring at an MR head incorporated in a disk storage system. If a read error occurs in data read by the MR head, a CPU executes a usual read retry operation. If the read error is not removed by the usual read retry operation, the CPU presumes that the read error is caused by the thermal asperity phenomenon occurring at the MR head. Then, the CPU controls the MR head to move to a CSS zone on the disk, thereby executing a TA removal operation so as to remove a fine particle such as dust attached to the MR head. In the TA removal operation, the rotational speed of the disk is reduced so that the MR head can be brought into contact with the disk in the CSS zone.

Abstract: A servo mark detection device includes a synchronizing circuit, first and second shift registers, a frame pattern detection circuit, a control circuit, and a servo mark comparator. The synchronizing circuit detects a peak of the signal amplitude of a data pattern and outputs a synchronization data signal synchronized with a clock. The first shift register sequentially stores the synchronization data signal and outputs a latch data signal. The detection circuit determines the frame pattern of the latch data signal, outputs a determination data signal, determines a phase shift of the latch data signal with respect to the clock, and outputs a phase correction signal. The control circuit outputs a frame pulse signal at a predetermined clock period, outputs a frame pulse signal at a timing corrected with respect to the predetermined clock period on the basis of the phase correction signal, and outputs a check window signal when a predetermined number of frame pulse signals are output.

Abstract: A circuit and method for detecting write-safe conditions for a magnetic storage device The circuit includes an electrical interconnect, a write-safe circuit, a write-driver circuit, a read amplifier and a read/write element. The electrical interconnect has a write path and a read path. A read element is coupled to one end of the read path, while the read amplifier is coupled to the other end of the read path. A write element is coupled to an end of the write path that is in proximity to the read element, while a write-output circuit is coupled to the other end of the write path. Preferably, the write element and the read element are part of a magneto-resistive head, such as a Piggyback-Magneto-Resistive head. The write-safe circuit, coupled to the read amplifier, detects a write-safe condition based on a signal induced into the read path by a write signal on the write path.

Abstract: A first digital information signal, such as a digital video signal, is recorded in MPEG encoded form in the form of first packets in first track portions (TP.sub.1) on a record carrier. Program information contained packets (P.sub.0 ') are also recorded in the first track portions. In a subsequent editing step, an additional information signal, such as an audio signal, is MPEG encoded into second packets and recorded in second track portions (TP.sub.2) of the tracks. In order to enable a reproduction of the video signal and the additional audio signal in a later reproduction step, the program information contained packets (P.sub.0 ') recorded in the first track portions are such that the program information indicates that the first packets and at least the second packets belong together.

Abstract: A method and apparatus for generating very small split tables from an even smaller amount of information preferably stored on a medium in a system track. The present invention takes advantage of the fact that the pattern of split data cells is periodic. Each split table can be generated upon initial application of power from a relatively few parameters stored in the system track. A method is provided by the present invention for generating each split table based upon the zone number, the number of track wedges within the period of the repeat pattern, the rate at which data is to be written in the zone and two additional parameters. In addition, the present invention is a method and apparatus for increasing the efficiency of the medium by adjusting the size of each zone to minimize the number of split data cells stored on the medium. In accordance with the present invention, the size of each zone is selected based upon the length of the repeat pattern.

Abstract: A read channel for use in a disk drive having an MR head. The read channel comprises a compensation device which has a high-pass filter (HPF) for compensating a thermal asperity (TA). The read channel suppresses level changes of a data signal which have resulted from TA disturbance present in the data signal. The read channel has a switch circuit connected to the input of the HPF, for canceling the DC undershoot present in the data signal. The switch circuit maintains the DC level of the data signal at zero level while a thermal asperity is being detected in the data signal.

Abstract: A Class IV Partial Response Maximum Likelihood data channel for analog signal processing of a disk drive signal in tracking mode includes a signal error generating circuit for "folding" the analog disk drive signal around the three PR-IV target values of +1, -1 and 0. Using the smaller error signal rather than the larger analog disk drive signal by which the disk drive signal deviates from the target values results in significant power saving with no reduction in electronic signal to noise ratio. An integrated error generating circuit generates both a gain error signal and a timing error signal from the folded error signal for feedback control of the data channel variable gain amplifier and variable clock oscillator. Shared processing of the timing and gain error signals results in power savings and simpler circuitry.

Abstract: A channel quality circuit, incorporated within a sampled amplitude read channel utilized in a magnetic storage system, for processing and accumulating performance data from the individual read channel components, wherein the performance data is used to calibrate the read channel to operate in a particular environment, to estimate the bit error rate of the storage system, and to detect defects in the magnetic medium. The channel quality circuit generates a test pattern of digital data which is written to the storage system. Then, as the test pattern is read from the storage system, the channel quality circuit accumulates performance data from the read channel components. The test pattern is used to generate expected samples and expected sample errors relative to the samples read by the read channel. Gating logic is programmed to accumulate only the particular performance data of interest. The channel quality circuit computes auto and cross-correlations, squared errors, and threshold comparisons.

Abstract: A servo decoder is disclosed for disc storage systems that operates according to a novel coding scheme capable of accurately decoding detected codewords representing servo track address during seek operations, even when the recording head flies between two adjacent tracks, and capable of correcting errors in the detected codedwords caused by noise in the read signal, such as inter-symbol interference. In a first embodiment, the coding scheme comprises an error correcting code (ECC) capable of correcting a predetermined number of bit errors in the detected codewords. To achieve the equivalent effect of a conventional Gray code, the codewords are arranged such that adjacent track addresses differ by a number of bits equal to the minimum distance of the ECC code. In a second embodiment, the servo code corrects certain minimum distance error events associated with a trellis type sequence detector.

Abstract: The present invention is a method and apparatus for positioning a dual element magnetoresistive (MR) head relative to a storage medium in a storage device. The MR head has first and second MR elements. The storage medium is mounted in the storage device to allow relative movement between the MR head and the storage medium. The storage medium includes servo information provided to induce first and second thermal responses in the MR elements. A controller is coupled to the MR head and controls the relative movement between the MR head and the storage medium using the first and second thermal responses in the MR elements.

Abstract: A disk resident system for managing defective data sector information in a defective data sector map in a headerless format magnetic disk device. The defective data sector map is stored in gaps between fields in the headerless disk format itself or in existing disk administration fields. The defective data sector map includes a plurality of binary digits that individually correspond to a defective or non-defective status of an individual data sector on at least one section of at least one track proximate to the defective data sector map. The defective data sector map can be minimized by compressing repetitive 0's or 1's in the map. ECC coding and/or other redundancy checks can be included to ensure validity of the defective data sector map.

Abstract: A method of judging a sector synchronous signal for a disk reproducing apparatus, includes a first step for decoding and storing a synchronous signal, a second step for comparing the decoded synchronous signal with a reference sector synchronous signal, a third step for assuming the detected synchronous signal to be a sector synchronous signal when the decoded synchronous signal and the reference sector synchronous signal are identical based on a result of the second step, a fourth step for judging whether the synchronous signal stored before the decoded synchronous signal indicates a desired state, and a fifth step for finally judging that the assumed sector synchronous signal is a sector synchronous signal based on a result of the fourth step.

Abstract: Servo-pattern information is magnetically recorded on a product disc by magnetic print-through from a master medium. The master servo-writing medium is brought into close proximity with the product "slave" disc, and the two are subjected to an external magnetic field which assists in transferring magnetic servo-patterns to the slave disc in a print-through process. The preferred external magnetic field alternates and rotates with respect to the master/slave combination. In an alternative product disc structure, the magnetic layer is magnetically altered in a servo-pattern configuration. Non-magnetic portions of the servo pattern are created which define both gray code and servo burst information for the product disc.

Abstract: A magnetoresistive transducer biasing technique that provides a uniform transducer biasing in a product. The technique provides biasing for transducer constant power dissipation, constant sensor current density biasing, constant sensor bias voltage, constant sensor temperature rise biasing, and constant effective magnetic biasing of a transducer.

Abstract: A MR head amplifier of the present invention prevents a base potential of a transistor which supplies a current to a MR element from changing in a moment when the MR element changes from a write-state to a read-state. The MR head amplifier includes a loop amplifier that has a non-inverted input terminal connected to one end of a first transistor which supplies a current to a MR element and an inverted input terminal connected to one end of a second transistor which is supplied with a constant current through a constant current source. An output terminal of the loop amplifier is feedback to a base terminal of the first transistor via a first switch and one end of a capacitor whose other end is connected to a ground is connected to an output terminal of the first switch. The loop amplifier includes a second switch connected between the output terminal of the first switch and the base terminal of the first transistor, the second switch being closed during read-state and opened during write-state.

Abstract: An improved write precompensation circuit for a read/write channel circuit and system is provided. Multiple data input signals are provided, each being clocked by a different clock. The data input signals are then multiplexed. Two, three or more data clock delays may be utilized to provide two, three or more data delays to achieve the write precompensation. Only one edge of a signal need pass through a multiplexer before the multiplexer may change state. The amount of delay may be user programmable.