Patent ID: 6108152
Filing Date: 2000-08-22
Classification: G11B

Abstract:
A format for a contiguous data block of a disc drive which employs an encoding scheme to encode n bit patterns of input user data into corresponding legal n+k bit patterns of encoded user data, the disc drive having a rotatable disc and a controllably positionable head used to store the encoded user data in the data block, the disc drive further having a read channel responsive to the head for recovering the encoded user data from the data block and decoding the encoded user data to output the original input user data, the data block format comprising:a user data field to which encoded user data are stored;a first sync field preceding the user data field having a first sync pattern for synchronizing the read channel to enable the read channel to recover the encoded user data from the user data field; anda second sync field preceding the user data field and disposed between the first sync field and the user data field having a second sync pattern different from the first sync pattern for synchronizing the read channel to enable the read channel to recover the encoded user data from the user data field when the first sync pattern fails to synchronize the read channel, wherein the first and second sync fields are separated within the data block by a sufficient distance to enable recovery of the encoded user data from the user data field when an anomalous condition prevents detection of the first sync pattern, and wherein the second sync pattern comprises an illegal n+k bit pattern to facilitate differentiation of the second sync pattern from the legal n+k bit patterns of the encoded user data in the user data field.