Granted Patent B1

US 8,917,469 · App. 13/614,894 · Granted Dec 23, 2014

Abstract

Claims (29)

1. A disk drive comprising:

a disk comprising a plurality of tracks defined by a plurality of servo sectors;

a head actuated over the disk; and

control circuitry operable to:

generate an estimated track ID representing an estimated radial location of the head;

generate a plurality of proximate track IDs having values proximate the estimated track ID;

generate a set of Gray codes each corresponding to the estimated track ID and the proximate track IDs, wherein each Gray code in the set of Gray codes comprises N bits, and M bits out of a high order of the N bits comprise the same value;

detect a Gray code in a first servo sector to generate a detected Gray code; and

correct an error in the detected Gray code by inverting at least one bit in the detected Gray code comprising a value that is different from the value of the corresponding bit in the M bits,

wherein:

the plurality of proximate track IDs extend from a −L proximate track ID preceding the estimated track ID to a +L proximate track ID following the estimated track ID;

L is an integer greater than one; and

the control circuitry is further operable to determine the M bits by comparing only the Gray code representing the −L proximate track ID to the Gray code representing the +L proximate track ID.

2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to convert a subset of the corrected Gray code into a partial track ID.

3. The disk drive as recited in claim 2 , wherein the control circuitry is further operable to convert a plurality of the lower order bits of the corrected Gray code into the partial track ID.

4. The disk drive as recited in claim 3 , wherein the control circuitry is further operable to combine the estimated track ID with the partial track ID to generate a detected track ID.

5. A method of operating a disk drive, the disk drive comprising a head actuated over a disk comprising a plurality of tracks defined by a plurality of servo sectors, the method comprising:

generating an estimated track ID representing an estimated radial location of the head;

generating a plurality of proximate track IDs having values proximate the estimated track ID;

generating a set of Gray codes each corresponding to the estimated track ID and the proximate track IDs, wherein each Gray code in the set of Gray codes comprises N bits, and M bits out of a high order of the N bits comprise the same value;

detecting a recorded Gray code in a first servo sector to generate a detected Gray code; and

correcting an error in the detected Gray code by inverting at least one bit in the detected Gray code comprising a value that is different from the value of the corresponding bit in the M bits,

wherein:

the plurality of proximate track IDs extend from a −L proximate track ID preceding the estimated track ID to a +L proximate track ID following the estimated track ID;

L is an integer greater than one; and

further comprising determining the M bits by comparing only the Gray code representing the −L proximate track ID to the Gray code representing the +L proximate track ID.

6. The method as recited in claim 5 , further comprising converting a subset of the corrected Gray code into a partial track ID.

7. The method as recited in claim 6 , further comprising converting a plurality of the lower order bits of the corrected Gray code into the partial track ID.

8. The method as recited in claim 7 , further comprising combining the estimated track ID with the partial track ID to generate a detected track ID.

Assignments (8)