摘要:
A measurement circuit is provided to obtain data for monitoring the quality of performance from a digital read channel. Elements of the digital read channel including a sequence detector are incorporated into an integrated circuit together with the measurement circuit. The measurement circuit relates digitized samples of readback data from a magnetic storage device to surrounding samples so that particular samples can be collected in accordance with their surroundings. The circuit includes a programmable time window which can be repeatedly opened for data collection. The circuit is designed to collect various types of data including the bit error rate, sample value, squared sample error, squared gain error, squared timing error, and the occurrences of sample error when it is outside an acceptable programmable threshold. The measurement circuit includes a signal generator for producing a test pattern that is first stored and then read to produce the digitized readback sample values. The measurement circuit also includes a conversion circuit for converting the test pattern to a sequence of expected sample values in accordance with a state machine model of the sequence detector. The sample value error results from a comparison of the readback sample value to the expected sample value.
摘要:
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. A defect detection filter detects particular defects in the media. In order to predict the bit error rate of the storage system, the channel quality circuit accumulates noise auto-correlation data, confidence metrics from a sequence detector, and cross-correlation of expected sample errors with actual sample errors.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, filters the sample values according to a desired partial response, extracts timing information from the filtered sample values, and detects an estimated data sequence from the filtered sample values using a trellis type sequence detector matched to the partial response. The trellis sequence detector comprises programmable detector levels which allows for maximum flexibility in matching the sequence detector to the partial response.
摘要:
A synchronous read channel having a single chip integrated circuit digital portion which provides digital gain control, timing recovery, equalization, digital peak detection, sequence detection, RLL(1,7) encoding and decoding, error-tolerant synchronization and channel quality measurement is disclosed. The integrated circuit accommodates both center sampling and side sampling, and has a high degree of programmability of various pulse shaping and recovery parameters and the ability to provide decoded data using sequence detection or digital peak detection. These characteristics, together with the error-tolerant sync mark detection and the ability to recover data when the sync mark is obliterated, allow a wide variety of retry and recovery strategies to maximize the possibility of data recovery. Various embodiments, including an embodiment incorporating the analog functions as well as the primary digital functions of the read channel in a single integrated circuit, and preferred embodiments utilizing a reduced complexity, programmable modified Viterbi detector supporting a broad class of partial response channels are disclosed.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, filters the sample values according to a desired partial response, extracts timing information from the filtered sample values, and detects an estimated data sequence from the filtered sample values using a discrete time sequence detector. Discrete time timing recovery within the read channel comprises a variable frequency oscillator (VFO) for generating a sampling clock. A center operating frequency of the VFO is adjusted through a programmable register which stores a digital center frequency setting. A phase error is computed from the sample values and combined with the center frequency setting to control the frequency and phase of the sampling clock at the output of the VFO.
摘要:
A synchronous read channel having a single chip integrated circuit digital portion which provides digital gain control, timing recovery, equalization, digital peak detection, sequence detection, RLL(1,7) encoding and decoding, error-tolerant synchronization and channel quality measurement is disclosed. The integrated circuit accommodates both center sampling and side sampling, and has a high degree of programmability of various pulse shaping and recovery parameters and the ability to provide decoded data using sequence detection or digital peak detection. These characteristics, together with the error-tolerant sync mark detection and the ability to recover data when the sync mark is obliterated, allow a wide variety of retry and recovery strategies to maximize the possibility of data recovery. Various embodiments, including an embodiment incorporating the analog functions as well as the primary digital functions of the read channel in a single integrated circuit, and preferred embodiments utilizing a reduced complexity, programmable modified Viterbi detector supporting a broad class of partial response channels are disclosed.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, filters the sample values according to a desired partial response, extracts timing information from the filtered sample values, and detects an estimated data sequence from the filtered sample values using a discrete time sequence detector. A Channel Quality circuit accumulates various signals generated by the read channel, such as sample errors, gain errors, timing errors, etc., for use in calibrating the read channel components and estimating the bit error rate.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, filters the sample values according to a partial response of the form (1-D)(1+D).sup.n where n>1, extracts timing information from the filtered sample values, and detects an estimated data sequence from the filtered sample values using a discrete time sequence detector.
摘要:
A filter for compensating discrete secondary pulse formations associated with a data stream of discrete main pulses produced from data read from magnetic media. The filter's impulse response comprises a center coefficient with side compensating coefficients for attenuating the secondary pulses when the input signal is convolved with the impulse response. The magnitude and delay of the compensation coefficients are programmable and are adaptively adjusted to optimize the impulse response for a given environment. In a traditional FIR embodiment, two delay lines are used to generate the two programmable delays between the center coefficient and side compensation coefficients. In the preferred embodiment, an IIR filter provides the two programmable delays using only one delay line thereby reducing the size and cost of the circuit. Also in the preferred embodiment, the data stream is interleaved into an even and odd data stream and processed in parallel by two filters in order to double the throughput. Further, the pre-cursor correcting portion of the filter can be disabled in order to avoid delaying the data stream while still canceling the post-cursor secondary pulses. The filter also comprises attenuation and adder means to match the coincident sample values in amplitude and add them to substantially eliminate the effect of the secondary pulses in the discrete data stream.
摘要:
A synchronous read channel having a single chip integrated circuit digital portion which provides digital gain control, timing recovery, equalization, digital peak detection, sequence detection, RLL(1,7) encoding and decoding, error-tolerant synchronization and channel quality measurement is disclosed. The integrated circuit accommodates both center sampling and side sampling, and has a high degree of programmability of various pulse shaping and recovery parameters and the ability to provide decoded data using sequence detection or digital peak detection. These characteristics, together with the error-tolerant sync mark detection and the ability to recover data when the sync mark is obliterated, allow a wide variety of retry and recovery strategies to maximize the possibility of data recovery. Various embodiments, including an embodiment incorporating the analog functions as well as the primary digital functions of the read channel in a single integrated circuit, and preferred embodiments utilizing a reduced complexity, programmable modified Viterbi detector supporting a broad class of partial response channels are disclosed.