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Fault-Tolerant Index Detection Pattern for Hard Disk Files

IP.com Disclosure Number: IPCOM000039266D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Hunt, WJ: AUTHOR

Abstract

The pattern is a redundant pattern (1-2-3-4-5) of magnetic transitions imbedded on the dedicated servo surface of a hard magnetic disk to generate a fault-tolerant index pulse. The pattern (1-2-3-4-5) of magnetic transitions is a separate and distinct index pattern which is written once per revolution on the dedicated servo surface of the hard disk. The pattern is written in the fill area (D) of the figure immediately before the index servo identification pattern, which is the pattern (A) just preceding "Index Servo ID" in the figure indicating the index signal. The index pattern consists of the five consecutive (1-2-3-4-5) patterns which are identical. The index signal is generated at the servo identification "Index Servo ID", following the detected index pattern consisting of the five identical patterns (1-2-3-4-5).

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Fault-Tolerant Index Detection Pattern for Hard Disk Files

The pattern is a redundant pattern (1-2-3-4-5) of magnetic transitions imbedded on the dedicated servo surface of a hard magnetic disk to generate a fault- tolerant index pulse. The pattern (1-2-3-4-5) of magnetic transitions is a separate and distinct index pattern which is written once per revolution on the dedicated servo surface of the hard disk. The pattern is written in the fill area (D) of the figure immediately before the index servo identification pattern, which is the pattern (A) just preceding "Index Servo ID" in the figure indicating the index signal. The index pattern consists of the five consecutive (1-2-3-4-5) patterns which are identical. The index signal is generated at the servo identification "Index Servo ID", following the detected index pattern consisting of the five identical patterns (1-2-3-4-5). The first sequence shown in the figure of servo ID
(A), servo bursts (B) and fill (C) is the normal pattern written on the servo surface of the hard disk. The next sequence is the index pattern written once per revolution of the hard disk and consisting of the (1-2-3-4-5) patterns. The servo recognition circuitry detects pulses that are generated at each magnetic transition by the servo channel. The time between pulses is measured and used to divide time durations into two classes, short (S) and long (L). Short durations are nominally servo-written at 300 nsec lengths, and long durations are nominally servo-written at 600 nsec lengths. The long and short durations L and S are clear from an inspection of the spa...