Patent ID: 7522363

Claim:
A medium storage device comprising: a head for either reading or writing data on a track of a storage medium where servo information, including servo synchronization marks, is written on one track with a predetermined interval; an actuator for positioning said head on a desired track of said storage medium which is rotating; a controller for controlling reading or writing data on said storage medium by said head at a timing synchronizing the rotation of said storage medium; and a processing unit for correcting the synchronization timing of said controller from an interval of said servo synchronization marks detected by said controller, wherein said processing unit judges the normalcy of the detection of said servo synchronization marks, calculates said interval of the servo synchronization marks if the judgment result is normal, and corrects a frequency of the synchronization timing of said controller based on said calculated interval, and wherein, if said judgment result is not normal, said processing unit calculates a space of said servo synchronization marks which is estimated by interpolation processing of the space of said servo synchronization marks in the past, and corrects the frequency of the synchronization timing of said controller based on said estimated servo synchronization marks.