US 6,052,248 A · Parity channel code for enhancing the operation of a remod/demod sequence detector in a d=1 sampled amplitude read channel

Abstract

A sampled amplitude read channel is disclosed for disk storage systems employing a run-length limited (RLL) d=1 channel code which compensates for partial erasure, and a parity channel code for enhancing the operation of a remod/demod sequence detector. During a write operation, after encoding the user data into codewords comprising the RLL d=1 constraint, the parity over one interleave of a block of NRZI bits is computed and two parity bits appended to form a parity codeword. For an even number of "1" bits in the block, the parity bits are set to "00". For an odd number of "1" bits in the block, the parity bits are set to "10" if the codeword ends with a "0" bit and to "01" if the codeword ends with a "1" bit, thereby maintaining the RLL d=1 constraint. Thus, a parity codeword will always comprise an even number of "1" bits (even parity). During read back, a parity syndrome is generated over a detected parity codeword; if the parity syndrome indicates the codeword comprises an odd number of "1" bits (odd parity), then the codeword is corrected according to the most likely error made by the remod/demod sequence detector. As a result, the remod/demod sequence detector of the present invention approaches the distance enhanced performance of matching a trellis state machine to the parity constraint, but with significantly less circuitry.

Claims25

Dependent claims

A sampled amplitude read channel for reading data recorded on a disk storage medium by detecting the data from a sequence of discrete-time sample values generated by sampling pulses in an analog read signal from a read head positioned over the disk storage medium, comprising:

(a) a sampling device for sampling the analog read signal to generate the discrete-time sample values;
and
(b) a discrete time sequence detector for detecting a preliminary sequence from the discrete-time sample values, comprising an interleave parity generator for computing a parity syndrome over one interleave of the preliminary sequence, the parity syndrome for correcting errors in the preliminary sequence.

A sampled amplitude read channel for reading run-length-limited (RLL) d=1 data recorded on a disk storage medium by detecting the data from a sequence of discrete-time sample values generated by sampling pulses in an analog read signal from a read head positioned over the disk storage medium, comprising:

(1) a sampling device for sampling the analog read signal to generate the discrete-time sample values;
(m) a timing recovery circuit, responsive to the discrete-time sample values, for generating synchronous sample values substantially synchronized to a baud rate of the recorded data;
and
(n) a remod/demod sequence detector for detecting the data from the synchronous sample values, comprising:
(i) a discrete time sequence detector, responsive to the synchronous sample values, for detecting a preliminary sequence in an NRZI format, the preliminary sequence having one or more errors;
(ii) an interleave parity generator for generating a parity syndrome over one interleave of the preliminary sequence;
(iii) a remodulator for remodulating the preliminary sequence into a sequence of estimated sample values;
(iv) an error value generator, responsive to the synchronous sample values and the estimated sample values, for generating a sequence of sample error values;
(v) an error pattern detector, responsive to the sequence of sample error values, for detecting a magnitude and location of the errors in the preliminary sequence;
and
(vi) an error corrector, responsive to the magnitude and location of the errors and to the parity syndrome, for correcting the preliminary sequence.

8 more elements

Dependencies are inferred from the claim text.

Parity channel code for enhancing the operation of a remod/demod sequence detector in a d=1 sampled amplitude read channel

Life of this patent

Parity channel code for enhancing the operation of a remod/demod sequence detector in a d=1 sampled amplitude read channel

Life of this patent

Abstract

Claims25