Patent ID: 7237178

Claim:
A hard disk drive system comprising: a hard disk drive comprising a channel; a channel detector that receives a first signal representing a channel sequence from the channel, and that produces a first detected sequence based on the first signal, wherein the first detected sequence comprises a plurality of symbols; a decoder comprising: an error-correction decoder that produces first data based on the first detected sequence when a number of symbols in error in the first detected sequence is less than, or equal to, a predetermined number, and that asserts a failure indication when the number of symbols in error in the first detected sequence is greater than the predetermined number; and a controller that, when the error-correction decoder asserts the failure indication for the first detected sequence, causes the channel detector to receive a second signal representing the channel sequence from the channel, and to produce a second detected sequence based on the second signal, wherein the second detected sequence comprises a plurality of symbols, and identifies corresponding symbols of the first and second detected sequences that differ; wherein the decoder produces second data based on the symbols identified by the controller and at least one of the first and second detected sequences.