Browse Prior Art Database

Redundant Servo Identification Mark

IP.com Disclosure Number: IPCOM000040237D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Rogelstad, WA: AUTHOR

Abstract

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.

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Redundant Servo Identification Mark

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. Encoding two separate SID patterns allows for one to be unreadable and still be able to generate the timing signals required to read the servo information (position data). The figure shows an example of a SID which has more than one recognizable pattern to detect and generate demodulator timing. It consists of a series of long and short (L and S) magnets. A pattern of L L L L S S indicates a valid first Servo ID; S L S L L L indicates a valid second Servo ID. Normally, the demodulator timings would be generated by the first SID, but if it is not detected for any reason, the timings could be generated using the second SID. The second SID would only be used if...