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US 8,284,510 B1Granted
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.
Claims13
A method comprising:
- recording time stamps for a repeating characteristic of a spindle back electromotive force (BEMF) signal;
- 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;
- and
- correcting the timing error, wherein the correcting the timing error comprises
- re-starting a phase locked loop (PLL) that locks a reference clock to the servo pattern on the machine readable medium, and
- re-aligning the timing for writing the servo pattern by using a sync mark of a servo pattern written on the machine readable medium,
- wherein the spindle BEMF signal comprises a digital signal, and
- wherein the repeating characteristic comprises a zero crossing of the spindle BEMF signal.
5 more elements
An apparatus comprising:
- a controller configured to control a spindle of a self-servo write (SSW) system;
- a SSW module communicatively coupled with the controller, the SSW module being configured (i) to record time stamps for a repeating characteristic of a back electromotive force (BEMF) signal received from the controller and (ii) to compare 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 the self-servo write (SSW) system;
- and
- a reference clock configured to latch the recorded time stamps, the reference clock being controlled by a phase locked loop (PLL) that is configured to lock the reference clock to the servo pattern on the machine readable medium,
- wherein the SWW module is further configured to correct the timing error by (i) re-starting the phase locked loop (PLL) and (ii) re-aligning the timing for writing the servo pattern by using a sync mark of a written servo pattern on the machine readable medium, and
- wherein the spindle BEMF signal comprises a digital signal and wherein the repeating characteristic comprises a zero crossing of the spindle BEMF signal.
3 more elements
Dependencies are inferred from the claim text.