Read errors treatment on the basis of error correction code and read channel - quality indicators

摘要

An apparatus and method for recovering from read errors detected by a read channel (70) in a sequence of data read from a disc (18) of a disk drive (10) by using read channel quality indicators to determine the appropriateness of using error correction in combination with other corrective actions utilized in the recovery process. Upon the detection of an uncorrected error in the retrieved data, the disk drive (10) enters a read recovery routine wherein one or more corrective actions (102, 122) are applied in an effort to resolve the error. One of the channel quality indicators comprises a channel quality measurements (108, 128) determined as the sum of the square of the sampled data bit error values recovered during the read operation. When the channel quality measurement is at or below a treshold value indicative that the probability of passing undetected erroneous data is at an acceptable level (110, 130), error correction is applied to the data (112, 138); otherwise, error correction is disallowed (118, 140). Additional channel quality indicators comprise erasure pointers (132) which identify a particular set of symbols that are suspected of containing a read error.