Detecting and recovering timing slips in a self servo write (SSW) system
AssigneeMarvell International Ltd.
InventorsDavid Rutherford, Man Cheung
Life of this patent
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Abstract
Embodiments of the present disclosure provide a method including recording time stamps for a repeating characteristic of a spindle back electromotive force (BEMF) signal and comparing one or more of the recorded time stamps for the repeating characteristic of the spindle BEMF signal with an expected value for the one or more recorded time stamps to detect a timing error associated with writing a servo pattern on a machine readable medium of a self-servo write (SSW) system. Other embodiments may be described and/or claimed.
Claims15
A method comprising:
- while writing a servo pattern on a machine readable medium rotating about a spindle,
- i) recording, over time, a plurality of time stamps associated with a characteristic of a back electromotive force signal generated as the machine readable medium rotates about the spindle, wherein the characteristic of the back electromotive force signal repeats over the time that the plurality of time stamps are recorded, and wherein the characteristic of the back electromotive force signal is expected to repeat at expected times over the time that the plurality of time stamps are recorded,
- ii) performing a comparison of one or more of the plurality of time stamps with one or more of the expected times that the characteristic of the back electromotive force signal is expected to repeat,
- iii) based upon the comparison, detecting a timing error associated with writing the servo pattern on the machine readable medium, and
- iv) based on the timing error, re-writing at least a part of the servo pattern that was previously written on the machine readable medium.
A self-servo write controller configured to control a spindle of a self-servo write system, the self-servo write controller comprising a self-servo write module configured to:
- while writing a servo pattern on a machine readable medium rotating about the spindle,
- i) record, over time, a plurality of time stamps associated with a characteristic of a back electromotive force signal generated as the machine readable medium rotates about the spindle, wherein the characteristic of the back electromotive force signal repeats over the time that the plurality of time stamps are recorded, and wherein the characteristic of the back electromotive force signal is expected to repeat at expected times over the time that the plurality of time stamps are recorded,
- ii) perform a comparison of one or more of the plurality of time stamps with one or more of the expected times that the characteristic of the back electromotive force signal is expected to repeat,
- iii) based upon the comparison, detect a timing error associated with writing the servo pattern on the machine readable medium, and
- iv) based on the timing error, re-write at least a part of the servo pattern that was previously written on the machine readable medium.
A self-servo write system comprising:
- a spindle;
- a machine readable medium configured to rotate about the spindle;
- and
- a self-servo write controller including a self-servo write module, wherein the self-servo write module is configured to
- while writing a servo pattern on the machine readable medium rotating about the spindle,
- i) record, over time, a plurality of time stamps associated with a characteristic of a back electromotive force signal generated as the machine readable medium rotates about the spindle, wherein the characteristic of the back electromotive force signal repeats over the time that the plurality of time stamps are recorded, and wherein the characteristic of the back electromotive force signal is expected to repeat at expected times over the time that the plurality of time stamps are recorded,
- ii) perform a comparison of one or more of the plurality of time stamps with one or more of the expected times that the characteristic of the back electromotive force signal is expected to repeat,
- iii) based upon the comparison, detect a timing error associated with writing the servo pattern on the machine readable medium, and
- iv) based on the timing error, re-write at least a part of the servo pattern that was previously written on the machine readable medium.
Dependencies are inferred from the claim text.