Low amplitude skip write detector
AssigneeSeagate Technology LLC
InventorsKendall Hayne Fung, Ewe Chye Tan
Life of this patent
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Abstract
A method and apparatus for detecting and respond to low-amplitude-write/skip-write events in a disc drive. The invention involves characterizing the gain factor of a variable gain amplifier embedded in the read path of a disc drive during at least two instances in which the read head passes over a servo sector, prior to a write event. Next the write event is executed. After the write event, the gain factor employed by the variable gain amplifier is acquired as the read head passes over the following servo sector. Finally, the acquired gain factor is compared to the characterization in order to detect a low-amplitude-write/skip-write event.
Claims19
A method of detecting write irregularities in a disc drive having a disc with one or more data sectors situated between consecutive servo sectors, and having a variable gain amplifier receiving a signal from a read head, a gain of the variable gain amplifier being controlled by a control signal, the method comprising steps of:
- characterizing the control signal during at least two instances during which the read head passes over a servo sector, prior to a write event;
- executing the write event;
- acquiring the control signal as the read head passes over an immediately following servo sector, after the write event;
- and
- comparing the acquired control signal to the characterization of the control signal in order to detect a write irregularity.
A method of detecting write irregularities in a disc drive having a disc with one or more data sectors situated between consecutive servo sectors, and having a variable gain amplifier receiving a signal from a read head, a gain of the variable gain amplifier being controlled by a control signal, the method comprising steps of:
- storing a first digital representation of the control signal as the read head passes over a first servo sector;
- storing a second digital representation of the control signal as the read head passes over a second servo sector;
- and
- obtaining an average of the first and second stored representations of the control signal;
- executing the write event;
- acquiring the control signal as the read head passes over a following servo sector, after the write event;
- and
- finding the difference between the acquired control signal and the average of the first and second stored representations of the control signal;
- comparing the difference against a threshold;
- declaring that a write irregularity has occurred, if the difference exceeds the threshold;
- and
- calling an off-track correction function, if the write irregularity event has occurred.
A method of detecting write irregularities in a disc drive having a disc with one or more data sectors situated between consecutive servo sectors, and having a variable gain amplifier receiving a signal from a read head, a gain of the variable gain amplifier being controlled by a control signal, the method comprising steps of:
- characterizing the control signal during at least two instances during which the read head passes over a servo sector, prior to a write event;
- executing the write event;
- acquiring the control signal as the read head passes over a following servo sector, after the write event;
- comparing the acquired control signal to the characterization of the control signal in order to detect a write irregularity;
- and
- calling an off-track correction function, if the write irregularity has occurred.
A disc drive comprising:
- a disc for magnetically storing data in one or more data sectors situated between consecutive servo sectors;
- a read head for reading data from the disc;
- a variable gain amplifier operably coupled to the read head for receiving a signal from the read head, the gain of the variable gain amplifier being controlled by a control signal;
- a gain controller operably coupled to the variable gain amplifier for generating the control signal;
- a microprocessor operably coupled to the gain controller, the microprocessor having access to a digital representation of the control signal, the microprocessor being programmed to
- characterize the control signal during at least two instances during which the read head passes over a servo sector;
- execute a write event;
- acquire the control signal as the read head passes over an immediately following servo sector, after the write event;
- and
- compare the acquired control signal to the characterization of the control signal in order to detect a write irregularity.
A disc drive comprising:
- a disc for magnetically storing data in one or more data sectors situated between consecutive servo sectors,
- a read head for reading data from the disc;
- a variable gain amplifier operably coupled to the read head for receiving a signal from the read head, the gain of the variable gain amplifier being controlled by a control signal;
- a gain controller operably coupled to the variable gain amplifier for generating the control signal;
- a microprocessor operably coupled to the gain controller, the microprocessor having access to a digital representation of the control signal, the microprocessor being programmed to:
- characterize the control signal during at least two instances during which the read head passes over a servo sector by storing a first digital representation of the control signal as the read head passes over a first servo sector, storing a second digital representation of the control signal as the read head passes over a second servo sector, and obtaining an average of the first and second stored representations of the control signal;
- execute a write event;
- acquire the control signal as the read head passes over the following servo sector, after the write event;
- and
- compare the acquired control signal to the characterization of the control signal in order to detect a write irregularity by finding a difference between the acquired control signal and an average of a first and second stored representation of the control signal, comparing the difference against a threshold, and declaring that a write irregularity has occurred, if the difference exceeds the threshold;
- and
- call an off-track correction function, if the write irregularity has occurred.
A disc drive comprising:
- a disc for magnetically storing data in one or more data sectors between consecutive servo sectors;
- and
- a means for determining a nominal distance between a read head and a disc surface, as the read head passes over a servo sector;
- a means for determining a fly height between the read head and the disc surface, as the read head passes over a servo sector immediately following a write event;
- and
- a means for comparing the nominal distance and the fly height.
Dependencies are inferred from the claim text.