Redundant Servo Identification Mark
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Servo ID marks can be encoded with two patterns which are used to generate demodulator timings. Having two patterns allows demodulator timings to be generated even if one of the patterns is unreadable. Servo ID (SID) marks are used in files that have sampled servo systems. The SID mark is used to identify the beginning of a servo field and to synchronize timing signals used to demodulate position information for controlling the position of the read/write heads. If a Servo ID mark is missing for any reason, it is not possible to read the position information from the Servo field. In the product, if multiple consecutive SID marks are missing, the file must recalibrate the actuator. This causes reduced file performance, and if the error is a hard error, the file is not usable.