Use of VFO Sync Fields for Servo Positioning Information in Disk Drives
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-31
Disclosed is a method of utilizing the pattern used to synchronize the file variable frequency oscillator (VFO) to the data field for both VFO synchronization and servo track following. The VFO sync field is a fixed frequency burst of information written on a disk file immediately ahead of the data field. The VFO is used to clock out the data in a disk drive when reading the data. This disclosure shows how that same VFO sync field can be used for the additional task of positioning the read/write heads. The VFO in the disk drive adjusts its phase to that of the VFO sync field so that the data that follows can be clocked out properly. Inverting the VFO sync field polarity can be done without affecting the ability to synchronize the VFO to readback the data.