Servo data recovery circuit for disk drive having digital embedded sector servo

摘要

A method and apparatus are provided for recovering servo information in a disk drive for positioning a data transducer head relative to concentric data tracks wherein the head reads user data encoded in a predetermined data code and reads servo information within plural servo sectors embedded in each data track defined on a storage surface of a rotating disk. The data tracks are arranged in plural groups of concentric tracks within concentric zones wherein each zone has a user data transfer rate selected in relation to disk radius, the servo information being recorded in at least three patterns within each embedded servo sector: a servo sync pattern, a user data code violating pattern, and a servo data bit pattern. A servo data recovery circuit implements the method comprising the steps of:   timing expected arrival of a servo sector with a sector timer,   at the expected arrival of the servo sector detecting a said servo sync pattern with a servo sync pattern detector,   detecting at least one said user data code violating pattern with a user data code violating pattern detector,   detecting recurrent servo data bit patterns as binary data bits with a data reader,   determining presence of a servo address mark with a master state machine following detection of said at least one user data code violating pattern,   upon detection of a servo address mark, restarting said sector timer,   accumulating within the master state machine the detected binary data bits in order to detect a track identification number, and   providing the track identification number to a head position servo loop for use in positioning the head relative to the data tracks during track seeking operations of the disk drive. The data reader forms an independent aspect of the present invention.