Disk drive seeking with a fixed rate clock when crossing servo zones to facilitate zoned servo sectors
View Patent ↗A disk drive is disclosed comprising a disk having a plurality of servo sectors defining a plurality of servo tracks that form a plurality of servo zones. The disk drive further comprises a head actuated radially over the disk for generating a read signal, and control circuitry operable to execute a seek operation. A fixed rate clock is generated, and a disk locked clock is generated and synchronized to the servo data rate of the servo zone the head is over. The disk locked clock is used to generate a servo timing window relative to a circumferential location of the head and the servo sectors. The control circuitry seeks the head from the first servo zone to the second servo zone, and switches to the fixed rate clock to generate the servo timing window while the head transitions from the first servo zone to the second servo zone.
1. A disk drive comprising:
a disk comprising a plurality of servo sectors defining a plurality of servo tracks,
wherein:
each servo sector comprises a servo sync mark;
the servo tracks form a plurality of servo zones; and
a servo data rate of the servo sectors in a first servo zone is different than a servo data rate of the servo sectors in a second servo zone;
a head actuated radially over the disk for generating a read signal; and
control circuitry operable to:
generate a fixed rate clock;
generate a disk locked clock synchronized to the servo data rate of the servo zone the head is over;
use the disk locked clock to generate a servo timing window relative to a circumferential location of the head and the servo sectors;
seek the head from the first servo zone to the second servo zone; and
switch to the fixed rate clock to generate the servo timing window while the head transitions from the first servo zone to the second servo zone.
2. The disk drive as recited in claim 1 , wherein the servo timing window comprises a servo gate window enabled as the head approaches one of the servo sectors.
3. The disk drive as recited in claim 1 , wherein the servo timing window comprises a sync mark window enabled as the head approaches the servo sync mark in one of the servo sectors.
4. The disk drive as recited in claim 1 , wherein the control circuitry comprises a first frequency synthesizer for generating the disk locked clock and a second frequency synthesizer for generating the fixed rate clock.
5. The disk drive as recited in claim 4 , wherein the control circuitry is further operable to program the first frequency synthesizer relative to the servo data rate of the servo zone the head is over.
6. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to switch to the fixed rate clock relative to when the servo timing window is enabled.
7. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to program the first frequency synthesizer to operate in the second servo zone after processing the last servo sector of the first servo zone.
8. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to switch to the fixed rate clock before the seek.
9. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to switch back to the disk locked clock after the head transitions to the second servo zone.
10. The disk drive as recited in claim 9 , wherein the control circuitry is further operable to switch back to the disk locked clock after the seek.
11. A method of operating a disk drive, the disk drive comprising a disk comprising a plurality of servo sectors defining a plurality of servo tracks, wherein:
each servo sector comprises a servo sync mark;
the servo tracks form a plurality of servo zones; and
a servo data rate of the servo sectors in a first servo zone is different than a servo data rate of the servo sectors in a second servo zone;
the disk drive further comprising a head actuated radially over the disk for generating a read signal, the method comprising:
generating a fixed rate clock;
generating a disk locked clock synchronized to the servo data rate of the servo zone the head is over;
using the disk locked clock to generate a servo timing window relative to a circumferential location of the head and the servo sectors;
seeking the head from the first servo zone to the second servo zone; and
switching to the fixed rate clock to generate the servo timing window while the head transitions from the first servo zone to the second servo zone.
12. The method as recited in claim 11 , wherein the servo timing window comprises a servo gate window enabled as the head approaches one of the servo sectors.
13. The method as recited in claim 11 , wherein the servo timing window comprises a sync mark window enabled as the head approaches the servo sync mark in one of the servo sectors.
14. The method as recited in claim 11 , wherein a first frequency synthesizer generates the disk locked clock and a second frequency synthesizer generates the fixed rate clock.
15. The method as recited in claim 14 , further comprising programming the first frequency synthesizer relative to the servo data rate of the servo zone the head is over.
16. The method as recited in claim 11 , further comprising switching to the fixed rate clock relative to when the servo timing window is enabled.
17. The method as recited in claim 11 , further comprising programming the first frequency synthesizer to operate in the second servo zone after processing the last servo sector of the first servo zone.
18. The method as recited in claim 11 , further comprising switching to the fixed rate clock before seeking the head.
19. The method as recited in claim 11 , further comprising switching back to the disk locked clock after the head transitions to the second servo zone.
20. The method as recited in claim 19 , further comprising switching back to the disk locked clock after the seek.