Abstract: A data signal comprising an even component and an odd component with differing amplitudes is received at a main automatic gain controller (AGC). The even component is adjusted by a first interleaved AGC and the odd component is adjusted by a second interleaved AGC such that even and odd component amplitudes are substantially equal. Amplitude adjusted even and odd components are recombined to define a data signal with components having substantially equal amplitudes. The even and odd components can be generated by a read transducer moving relative to a magnetic storage medium comprising tracks defined by discrete and spaced-apart recording bits arranged in an interspersed pattern. A read channel separates the data signal into even and odd samples such that a gain can be independently adjusted for each of the even and odd samples to compensate for asymmetry between the even and odd samples.

Abstract: A data signal comprising an even component and an odd component with differing amplitudes is received at a main automatic gain controller (AGC). The even component is adjusted by a first interleaved AGC and the odd component is adjusted by a second interleaved AGC such that even and odd component amplitudes are substantially equal. Amplitude adjusted even and odd components are recombined to define a data signal with components having substantially equal amplitudes. The even and odd components can be generated by a read transducer moving relative to a magnetic storage medium comprising tracks defined by discrete and spaced-apart recording bits arranged in an interspersed pattern. A read channel separates the data signal into even and odd samples such that a gain can be independently adjusted for each of the even and odd samples to compensate for asymmetry between the even and odd samples.

Abstract: A method of decoding a turbo product code (TPC) code word comprises iteratively decoding the TPC code word using an iterative decoder. The method further comprises terminating the iterative decoding when the TPC code word satisfies a cyclic redundancy check (CRC). The TPC code word can include a plurality of square code blocks of user data, with CRC data bits appended to one of the plurality of code blocks instead of replacing user data within the code blocks. Apparatus for implementing the method are also provided.

Abstract: A method of decoding a turbo product code (TPC) code word comprises performing a cyclic redundancy check (CRC) on each of a plurality of code blocks of the TPC code word. The bits of code blocks of the TPC code word which pass the CRC are assigned an artificially high probability confidence measure, such as an artificially high log-likelihood ratio. Assigning these bits an artificially high probability confidence measure allows an iterative process, between a soft decision algorithm and a TPC decoder, to be less complex and to converge on a correct decoding solution more quickly. Apparatus for implementing the method are also provided.

Abstract: A sequence generator is configured to be re-initialized to a value selected derived from a candidate group that is derived from a predetermined value. If and when the re-initializing is performed, it is fully performed within about one clock cycle of setting the sequence generator to the predetermined value. The sequence generator is optionally initialized by a local processor to which it is operatively coupled, after which the processor receives one sequence value each cycle.

Abstract: A sequence generator is configured to be re-initialized to a value selected derived from a candidate group that is derived from a predetermined value. If and when the re-initializing is performed, it is fully performed within about one clock cycle of setting the sequence generator to the predetermined value. The sequence generator is optionally initialized by a local processor to which it is operatively coupled, after which the processor receives one sequence value each cycle.

Abstract: A method of decoding a turbo product code (TPC) code word comprises iteratively decoding the TPC code word using an iterative decoder. The method further comprises terminating the iterative decoding when the TPC code word satisfies a cyclic redundancy check (CRC). The TPC code word can include a plurality of square code blocks of user data, with CRC data bits appended to one of the plurality of code blocks instead of replacing user data within the code blocks. Apparatus for implementing the method are also provided.

Abstract: A method of decoding a turbo product code (TPC) code word comprises performing a cyclic redundancy check (CRC) on each of a plurality of code blocks of the TPC code word. The bits of code blocks of the TPC code word which pass the CRC are assigned an artificially high probability confidence measure, such as an artificially high log-likelihood ratio. Assigning these bits an artificially high probability confidence measure allows an iterative process, between a soft decision algorithm and a TPC decoder, to be less complex and to converge on a correct decoding solution more quickly. Apparatus for implementing the method are also provided.

Abstract: A transition overshoot of the record current is usual to compensate record head efficiency loss at high frequencies. Recording compatibility is achieved by decreasing the record current overshoot at the digital data signal transitions as the head gap depth decreases due to wear. Additionally, the different gap depth record heads of different head efficiencies require different optimum record current levels to provide maximum signal-to-noise ratio in the reproduced signal. The head gap depth thus is monitored by means of the optimum record current level without actually measuring the gap depth. The desired amount of overshoot is adaptively adjusted to the gap depth during the recording process by tracking the overshoot to the optimum record current level derived by adjusting the record drive level signal. Recording compatibility between different gap depth heads is achieved using the existing normal record current optimization process during recording.

Abstract: A pipelined Viterbi decoder includes a plurality of circuit stages and a synchronous clocking arrangement for controlling the operations of the circuits within each stage. Specifically, an input stage converts multi-level input signals into streams of even and odd digital data samples. A parallel-precomputation stage adaptively establishes a threshold range for each sample, while a sequence detection stage designates one of the multiple levels for that sample and then determines the validity of that designation. Validity is determined in accordance with the sequence property of alternate samples in multi-level coding. Violations of the sequence property are corrected by a sequence correction stage so that valid, coded data and clock signals are provided at the outputs of the decoder.

Abstract: Two closely spaced magnetostatically coupled magnetoresistive elements are arranged with their respective planar surfaces in parallel. A nonmagnetic insulating material is interposed between the elements to prevent exchange coupling. Sense current flows simultaneously through both elements in the same direction and in perpendicular to the easy axis of magnetization. In response to signal fields applied in parallel with the sense current flow demagnetization components in the easy axis direction cancel. The output signal of the transducer is independent of recording track width and free of Barkhausen noise.