US 2015/0279398 A1Published application

Locking a Disk-Locked Clock Using Timestamps of Successive Servo Address Marks in a Spiral Servo Track

AssigneeLSI Corporation

InventorsXiangdong Fan, Songtao Chen

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Abstract

Described embodiments provide a magnetic mass storage device with a system clock phase-locked to servo address marks on the magnetic disk. A head sequentially reads multiple adjacent servo address marks in a spiral track of servo address marks. When a servo address mark detector detects a mark, the count value of a counter driven by the system clock is sampled and held by a latch. A system clock synthesizer calculates differences in value between successively sampled count values from the latch, averages the differences in value to create an average difference value, and normalizes a difference between the average difference value and a target value to create a phase error value. The phase of the system clock is updated using the phase error value.

Claims20

Dependent claims

A mass storage system comprising:

a rotating magnetic storage media having adjacent servo address marks written in a spiral pattern of servo address marks on the storage media;
a head configured to read data and servo information stored on the media, the head and the spiral pattern configured such that the head reads a plurality of adjacent servo address marks each time the head encounters the spiral pattern of servo address marks;
a servo address mark detector coupled to the head and configured to detect servo address marks when read by the head;
a counter driven by a system clock;
a latch responsive to an output of the servo address mark detector and configured to sample a count value of the counter when triggered by the servo address mark detector;
and
a disk-locked clock synthesizer, responsive to the latch, configured to generate the system clock;
wherein the synthesizer, as the head reads the plurality of adjacent servo address marks, is configured to:
calculate differences in value between successively sampled count values from the latch;
average the differences in value to create an average difference value;
normalize a difference between the average difference value and a target value to create a phase error value;
and
updating a phase of the system clock in response to the phase error value.

10 more elements

In a mass storage system having a rotating magnetic storage media and head over the media for reading data and servo information thereon, the rotating magnetic storage media having adjacent servo address marks written in a spiral pattern of servo address marks on the storage media, the system having a counter driven by a system clock, a method for phase locking the system clock to servo address marks on the media comprising the steps of:

reading, by the head, a plurality of adjacent servo address marks each time the head encounters the spiral pattern of servo address marks;
detecting each of adjacent servo address marks read by the head;
sampling the counter to obtain a count value thereof each time a servo address mark is detected;
calculating differences in value between successive sampled count values from the latch;
averaging the differences in value to create an average difference value;
normalizing a difference between the average difference value and a target value to create a phase error value;
and
updating a phase of the system clock in response to the phase error value.

5 more elements

Dependencies are inferred from the claim text.