Patent ID: 8451697

Claim:
A disk drive comprising: a disk comprising a plurality of spiral tracks, each spiral track comprising a high frequency signal interrupted at a predetermined interval by a sync mark; a head actuated over the disk; and control circuitry operable to: use the head to read the spiral tracks to generate a read signal representing spiral track crossings; and process the spiral track crossings to first seek the head over a plurality of concentric tracks defined by the spiral tracks, and during the first seek: first open a first demodulation window in response to a first window offset during a first revolution of the disk, wherein the first demodulation window corresponds to the head approaching a first spiral track; use the head to read the first spiral track to generate a first spiral track crossing; generate a first window position error signal (PES) representing a difference between a target framing of the first demodulation window around the first spiral track crossing and a detected framing of the first demodulation window around the first spiral track crossing; adjust the first window offset in response to the first window PES; and second open the first demodulation window in response to the adjusted first window offset during a second revolution of the disk.