Patent ID: 7158324

Claim:
A method for partial response maximum likelihood (PRML) data detecting in a magnetic recording storage device, said method comprising the steps of: (a) measuring write-read channel responses of said storage device to all nonzero binary combinations of a given length; (b) decoding applied user data according to a Viterbi algorithm using said previously measured responses as expected samples for branch metric calculations in said algorithm; wherein said responses measuring step comprises the sub-steps of: (a) writing to a magnetic data recording disk a test pattern representing reiteration of a basic blocks, each block including a preamble, an address mark and periodically repeated pseudo-random seciuences containing all nonzero binary combinations of a given length; (b) reading the test pattern from the disk to generate a read-back test signal; (c) processing the read-back test signal to generate write-read channel responses to all nonzero binary combinations of the given length; wherein said read-back test signal processing comprises the sub-steps of: (a) acquiring clock frequency and initial clock phase during each preamble in the read-back test signal without clock phase correction up to next preamble appearance; (b) using said acquired clock frequency and clock phase to build a set of read-back test signal samples, said set containing exactly one sample per test pattern bit; (c) separating out said samples as responses to different binary combinations in the pseudo-random part of each of said basic blocks, and averaging samples corresponding to the same binary combination over the entire test pattern.