Dynamic magnetic information storage or retrieval – General processing of a digital signal – In specific code or form
Reexamination Certificate
1999-06-22
2003-04-15
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
In specific code or form
C360S077040
Reexamination Certificate
active
06549351
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to the field of disk drive systems, and in particular, to disk drive systems and circuitry that encode auxiliary data using polarity reversal pulses.
2. Statement of the Problem
Disk drive systems include control circuitry and a disk device. The disk device stores user data, servo data, and auxiliary data. A computer system exchanges the user data with the control circuitry. The control circuitry exchanges the user data with the disk device for storage. To facilitate these data exchanges, the disk device reads and transfers servo data to the control circuitry. The servo data includes position information, such as a timing mark, head number, and cylinder number. The control circuitry uses the servo data to locate data on the disk device. The disk device also reads and transfers auxiliary data to the control circuitry. The auxiliary data typically follows the servo data on the disk. The control circuitry uses the auxiliary data to control the disk device. For example, the auxiliary data may include information that is used to compensate for defects in the disk device.
To write the auxiliary data to the disk device, the control circuitry first converts the auxiliary data into encoded signals. The control circuitry then controls the disk device to create magnetic transitions on the disk device that correspond to the encoded signals. To read the auxiliary data, the control circuitry controls the disk device to detect the magnetic transitions. The control circuitry then detects the encoded signals from the magnetic transitions and decodes the encoded signals into the auxiliary data.
Repeatable Run-Out (RRO) occurs when the data track on the disk surface does not appear to form a circle as the disk surface spins. If the RRO is substantial, portions of the data may not even appear proximately under the head causing a failure of the disk drive system. In some disk drive systems, the auxiliary data is RRO data. The RRO data is typically an integer that indicates the amount of RRO error for that area of the disk surface. The disk drive system uses the RRO data alter the position of the head keeping it over the non-circular data track.
As the disk surface spins, the head detects the magnetic transitions on the disk surface and transfers an analog read signal representing these transitions from the disk device to the read channel in the control circuitry. The read channel samples and filters the analog read signal. The read channel then processes the filtered samples to detect encoded signals. The read channel decodes the encoded signals into data bits and transfers a resulting bit sequence containing the servo data and the RRO data to servo control. The servo control processes the servo and RRO data to provide a position control signal to the position system, and in response to the position control signal, the position system positions the head over the appropriate point above the spinning disk surface. In particular, the servo control processes the RRO data to adjust the position of the head to compensate for RRO error.
The RRO data may use PR4-like encoding where a “1” is encoded as “1 1 −1 −1”, and a “0” is encoded as “0 0 0 0”. This encoding associates “1 1” with a rising edge magnetic transition, “−1 −1” with a falling edge magnetic transition, and “0 0” with no magnetic transition.
Unfortunately, disk drive systems cannot effectively exchange user data with the computer system when RRO error causes a loss of data. It should be appreciated that detecting RRO data is critical to the operation of the disk device, and to the effectiveness of the computer system. Thus, improved encoding techniques that provide better bit error rates when detecting RRO data would improve the operation of disk drive systems and computers.
Given the enormous growth in the demand for computer data storage, there is an acute need to continually improve the performance of disk drive systems. In particular, solutions are needed to reduce problems with RRO data detection. These solutions will provide for faster and more accurate data exchanges between the disk drive system and the computer system.
SUMMARY OF THE SOLUTION
The invention solves the above problem by providing improved disk drives and control circuitry that decode auxiliary data having polarity reversal pulses. The invention provides improved bit error rates with twice the decision distance of Gray coding because of the polarity reversal. The invention improves the operation of disk drives and computers by providing faster and more accurate data exchanges.
The invention includes disk drive circuitry, systems, and methods. The disk drive system comprises control circuitry and a disk device. The disk device transfers a read signal representing user data, servo data, and auxiliary data to the control circuitry. The control circuitry detects encoded signals representing “0” and “1” auxiliary data bits from the read signal. The control circuitry then decodes the encoded signals into the auxiliary data bits. The encoded signals representing the “0” auxiliary data bits have opposite polarity from the encoded signals representing the “1” auxiliary data bits. Polarity reversal pulses are placed between consecutive encoded signals with opposite polarities. The auxiliary data bits could be repeatable run-out data that is processed to generate a position signal that the disk device uses to compensate for repeatable runout error.
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Cirrus Logic Inc.
Hudspeth David
Slavitt Mitchell
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