Storage Technology Corporation

Brahim Lekmine

Donald L Millican

Joe Kent Jurneke

Douglas A Gunther

A data channel monitor is provided for a data channel that converts analog signal data to binary digital bits. The monitor allows the quality of the data detected to be measured in conjunction with predetermined processing steps performed in the data channel. The channel monitor obtains channel data and uses the data to determine detection margins, which are a measure of the data quality. The detection margins are compared with an acceptable value(s). Error references are generated if a detection margin is outside an acceptable range. The data monitor also preferably includes a diagnostic capability wherein all detection margins may be stored for off-line analysis whenever the data channel is placed in diagnostic mode.

Data quality analysis in a data signal processing channel

A data channel is provided that includes a digital decoder that receives a dynamically determined tracking threshold value. The tracking threshold value has a voltage amplitude used by the decoder in decoding a digital voltage signal into binary data. The digital signal is generated using an analog voltage signal that represents data read from a storage medium, such as a magnetic tape or disk. The present method is able to generate appropriate tracking threshold values even during sudden changes in the voltage amplitudes associated with the digital signal. In dynamically determining tracking threshold values, an averaging method with error recovery is employed, that is independent of the particular encoding used with the stored data. For each inputted digital voltage signal that represents a binary bit, a comparison is made between it and a current accepting value. Unless the digital voltage signal is at least equal to the accepting value, it is not used in computing a new tracking threshold value. A running average value, based on a predetermined number of the most recently accepted digital voltage signal amplitudes, is determined. An updated tracking threshold value is then determined from the current average value. A feedback loop is also utilized whereby an updated accepting value is determined to be used in accepting/rejecting further signal inputs. The error recovery is employed to decrease the accepting value if a predetermined number of consecutively received digital voltage signals are rejected.

Digital decoding using dynamically determined tracking threshold values

A circuit and method for correcting peak signal shifts in analog signals representing binary data bits that avoids the need for write precompensation techniques. Three different sample values (an early, on-time, and late) are computed for the signal representing each read bit. The on-time signal value of each data bit of an n-bit sequence is used if no data corruption is detected. If a corrupted data bit is detected due to an early or late peak signal shift of an adjacent binary 1, the early or late signal value of the corrupted data bit is used rather than the on-time signal value of the corrupted bit. The corrected data bit sequence is then passed on to a utilization circuit, such as a read data detector, which uses error correcting techniques and the like to determine with precision whether each data bit is a binary 1 or a .0..

Bit shift post-compensation using sampled data prequalifier

A digital data decoder is provided that combines Viterbi algorithms and a run-length code constraint. The combined Viterbi detection and code constraint does not limit the bits that can be analyzed in determining the binary state of the bit currently being detected. The logic associated with the code constraint is not enabled unless actual data is being decoded.

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Denver, CO, United States of America

Brahim Lekmine