Abstract: Methods of encoding and decoding as well as an encoder and decoder are provided for encoding data words into codewords and decoding codewords into data words. The data words are encoded by mapping each data word into a number of data segments. Each data segment is then encoded to form a codeword segment that has the same number of bits as the data word segment. The codeword segments are concatenated to form the codeword. The codewords are decoded by decoding individual codeword segments into data word segments that are the same size as the codeword segments. The data word segments are then mapped into the data word, which has fewer bits than the total number of bits across all data word segments.

Abstract: An encoder and method of encoding data words are provided, which map a block of at least one of the data words into an error correction code (ECC) code word. The ECC code word is defined by a plurality of multiple-bit ECC symbols which are separated by boundaries. Bit patterns are constrained from occurring in the ECC code word based on a relative location of the bit patterns to the boundaries.

Abstract: A second order filter-delay element for use in a generalized analog transversal equalizer is described which provides phase and group delay responses equivalent to low-pass filters of third and fourth order. In addition, the filter-delay element provides sufficient values of delays required for proper operations of the analog generalized transversal equalizer despite having a low order. In addition, a method of generating the lower order filter-delay element is described. Also, a circuit embodying an active C-transconductor realization of a second order filter-delay element for use in a generalized analog transversal equalizer with a transfer function designed as a result of performing the method is described.

Abstract: Encoding and decoding systems and methods for digital data in 24 bit sequences. An encoder generates state variables as a function of four or fewer bits of the 24 bit sequence, and encodes the sequence into 11 and 14 bit codewords. After transmission, the 11 bit and 14 bit codewords are decoded using recovered state variables. The encoding places a run length limit (RLL) of k=7 on a 25 bit codeword comprised of the 11 and 14 bit codewords to limit runs of zeros. Each of the 11 bit and 14 bit codewords are preferably also encoded with a run length limit of interleaved bits is i=7. The encoding and decoding systems and methods can be applied to a magnetic disc drive.

Abstract: A detector is used in detecting data encoded in a read signal received from a storage channel. The detector includes a Viterbi detector having a time-invariant structure configured to detect the data encoded according to a code having time varying constraints.

Abstract: The present invention provides a method and apparatus for detecting data received from a magnetic storage channel having a channel pulse response represented by a polynomial including intersymbol interference (ISI) terms. The detector includes a Viterbi detector corresponding to a trellis structure having states connected by branches having associated branch metrics. In one embodiment, the Viterbi detector includes a branch metric calculator component configured to calculate a branch metric associated with each of the plurality of branches by removing a contribution to the branch metric associated with a predetermined ISI term.

Abstract: An encoder and a method of encoding successive data words into successive code words for transmission through a channel is provided. The encoder divides each successive data word into first and second portions. The first portion of each successive data word is mapped into a corresponding first code pattern and a corresponding state variable according to a selected code. A second portion of each successive data word is mapped into a corresponding second code pattern that is associated with the state variable, according to the selected code. The first and second code patterns are combined to form each of the successive code words. The successive code words are concatenated to form an encoded bit stream having a plurality of bit positions.

Abstract: A storage device includes a storage medium, write element and a data input. A first encoder provides an encoded data output as a function of a first portion of the data input. The first encoder also provides a state output. A second encoder provides a second encoded data output as a function of the plurality of data input and as a function of the state output. The first and second data outputs are coupled to the write element for writing information onto the storage medium. In addition, a similar technique is used for a block decoder.

Abstract: An apparatus and method are disclosed for reducing the effects of thermal asperities and other anomalous conditions on disc drive read operations. An improved data block format is provided having first and second sync fields in which sync patterns are stored, the first and second sync fields being separated by a selected distance within the data block. The sync pattern of the second sync field enables synchronization of a disc drive read channel to the user data in the data block when the read channel fails to be synchronized by the sync pattern of the first sync field. In one embodiment, control information used by the read channel to prepare for receipt of the user data is stored in a field between the first and second sync fields; in an alternative embodiment, a portion of the user data is stored between the first and second sync fields.

Abstract: A detector in an informational handling system and a method of detection is provided. An input circuit is used to receive an input signal. A second circuit determines boundaries based on the input signal. However, at least two of the boundaries specified by the second circuit are monotonically related to each other. The detector can be implemented in a magnetic disc drive. A read circuit is operably coupled to the disc to read data stored on the disc. The read circuit includes an input circuit, a boundary calculation circuit, and a logic circuit operably coupled to one another. The input circuit serves to receive the data and provide an input to the boundary calculation circuit. The boundary calculation circuit calculates several boundaries based on the input. At least two of the boundaries are monotonically related. The boundary circuit provides an output to the logic circuit which provides a binary decision.

Abstract: A method and apparatus for encoding data produces a code stream of code words, where each code word includes two subsets of code bits. Each subset of code bits is constrained by a different maximum transition run constraint. In an alternative embodiment, the method and apparatus produces a code stream comprised of alternating even bit locations and odd bit locations, where the even bit locations are constrained by a different maximum run length constraint than the odd bit locations.

Abstract: An encoder and a method of encoding successive data words into successive code words having alternating code word lengths. Each code word has a plurality of bit locations. A first maximum transition run constraint is imposed on a first set of the bit locations, wherein each bit location in the first set is spaced S bit locations apart from one another, and S is an integer greater than one. A second maximum transition run constraint, which is different than the first maximum transition run constrain, is imposed on a second set of the bit locations, wherein the second set comprises each of the bit locations that are not in the first set. The alternating code word lengths and the value of S are defined such that corresponding bit locations in successive code words have the same maximum transition run constraint.

Abstract: An information handling system, such as a magnetic disk drive, includes a data channel which has a method and apparatus for detecting binary symbols from a received signal occurring at high data rates. The data channel includes a detector that has two inputs. The detector has a first portion which determines a first estimate of a binary input. The second portion, operating in parallel with the first portion, determines two conditional estimates for a second binary input. The estimate for the second binary input is selected after the first estimate is determined. The first and second estimates for the first and second binary inputs are then output from the detector. Each of the first and second portions of the detector uses a three dimensional observation space with orthogonal coordinate axes. Each of three consecutive synchronous observation samples of the received signal corresponding unambiguously to an axis in the observation space.

Abstract: Data is detected from a disc in a disc drive and provided as a sampled read signal including data samples provided in a plurality of time intervals. A signal space detector is configured to detect the data, wherein the data is encoded according to a code having a time varying maximum transition run constraint which varies between a first and a second constraint over a plurality of time intervals. The detector is configured to receive an input sample including a first plurality of terms indicative of one of a plurality of possible data symbols. One of the plurality of possible data symbols is eliminated based on the first constraint when the input sample then being detected is constrained by the first constraint, to provide a second plurality of remaining possible data symbols. An estimated data value is determined which corresponds to the input sample then being detected, by determining which of the second plurality of remaining possible data symbols is within a predetermined range of the input symbol.

Abstract: A method and apparatus for writing and reading servo data placed on a plurality of disk surfaces to minimize the degree of overlap of headers written or read by each write/read channel. Time division de-multiplexing (selecting) the writing of servo data to disk surfaces from each write/read channel and time division multiplexing the reading of servo data from the staggered headers contained on the disk surfaces coupled to each write/read channel increases the number of surfaces written to or read in a single rotation by each write/read channel. Disk surfaces are coupled to the write/read channels in groups to minimize the number of rotations required to write to or read from all the surfaces contained in the groups. Groups of surfaces may be sub-grouped. The headers of sub-groups are interleaved so that portions of the header written in a separate disk pass whose length is less than half the total length of the header may be written or read in the same rotation as another group of surfaces.

Abstract: A method and apparatus for optimizing the track seeking operation of disc drives by adaptively changing the seek velocity profile in response to the actual performance of the drive during track seeking operations based upon the amount of head overshoot and the actuator power dissipation.

Abstract: A data processing system records information on magnetic disks in a format in which sector headers, which include embedded servo information, are radially aligned and recorded at a single frequency and data are recorded at various band-related frequencies. The system records sector headers at a frequency which is optimal for the recording of address information in the shortest sector and records the data at frequencies which are optimal for the recording of information in the disk space allocated to the data portion of the various lengths of sectors. The system synchronizes to the headers, using conventional embedded servo synchronization methods, and produces header timing signals. It can then use the same header timing signals to locate and interpret the headers on different tracks, since the header frequency and the location of the headers are the same in every track. The system may record the data portions of the sectors at frequencies which are related to the header frequency by ratios of small integers.

Abstract: A data decoding system includes a data retrieval device which retrieves encoded data from a mass-storage device and transmits the data to a serial-to-parallel shift register. The shift register, operating at the data transfer rate, converts the encoded data to a parallel stream of bit-pairs. The bit-pairs are then transmitted, over parallel lines, to a second shift register which is operating at one-half the data transfer rate. The second shift register stores a sufficient number of the bit-pairs to constitute a byte of binary data when decoded. Once enough bit-pairs are stored, a ROM, operating at a rate which is slower than the data transfer rate, decodes the information to form a byte of binary data. The system utilizes a data retrieval system with a high data transfer rate and processing circuitry with a reduced bandwidth requirement to produce decoded data at a rate which is comparable to the data transfer rate.

Abstract: A data decoding circuit which receives an input signal comprising a sequence of pulses and generates a digital data output signal and timing signals in response thereto. The circuit includes a phase-locked loop which generates timing signals in response to the input signal and an offset signal from a data separator circuit. The data separator circuit generates the digital data output signal and the offset signal, which measures the degree of correlation between the input signal as received by the data separator and the timing signal from the phase-locked loop, thereby obviating the need to match the data separator circuit closely to the phase-locked loop.

Abstract: The invention encodes magnetic disk sector addresses using a large distance, "d", Reed-Solomon code to produce code words which vary by at least "d" symbols for any two different encoded addresss. The result of the encoding is a set of redundancy symbols, which are usually associated with error correction. These symbols are appended to the address symbols to produce address code words. An address code word read from a disk can contain up to (d-1)/2 errors and still be identified as the correct sector address. To protect the encoded sector address from synchronization errors the address code words are further encoded by adding them to a coset leader to produce header code words. The header code words are then recorded in the address portions of the sectors. When a header code word is read from a sector, the coset leader is subtracted from the header code word to produce an address code word. The address code word is then compared with the address code word for the specified address.