Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of the amplifier
Reexamination Certificate
1999-07-01
2001-10-16
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of the amplifier
C360S061000, C360S063000, C360S031000, C714S820000
Reexamination Certificate
active
06304403
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to disc drive data storage systems. More particularly, the present invention relates to circuits for detecting and signaling if multiple preamplifiers are concurrently selected.
BACKGROUND OF THE INVENTION
In disc drives, digital data is written to and read from the surfaces of one or more discs. Read and write operations are performed through a transducer which is typically carried on a slider body. The slider and the transducer are sometimes collectively referred to as a data head, and typically a single data head is associated with each data storage surface. The communication to and from the data heads is performed by a read/write preamplifier. High storage-capacity disc drives typically have a large number of data heads and thus have multiple read/write preamplifiers. Each read/write preamplifier typically drives a plurality of individual data heads, usually on a multiplexed basis. Typical read/write preamplifiers have a variety of fault detectors which monitor the operation of the preamplifier and send a fault signal to the drive controller if a fault condition occurs.
In a typical disc drive, an actuator operates in a servo system. The actuator moves the data head radially over the disc surface for track seek operations and holds the transducer directly over a track on the disc surface for track following operations. A servo controller samples the position of the data heads relative to some reference point and generates an error signal based upon the difference between the actual position and the reference position. This error signal is then used to drive the data head to the desired reference point. In one type of servo system, each track on a disc includes servo position information in a block of data referred to as a header. As the trend in the disc drive industry is to increase the efficiency of storing the user's data, the so-called “headerless” track formats are being considered. These formats allow more of the disc space to be used for the user's data, as opposed to servo and track information. However, these headerless track formats raise additional difficulties for guaranteeing data integrity, as the header formerly served to ensure that data was being written to the intended track.
The present invention provides a means of improving data integrity and offers other advantages over the prior art.
SUMMARY OF THE INVENTION
The present invention relates to read/write preamplifier circuits which reduce the probability of data being written to the wrong location on a disc.
One embodiment of the present invention is directed to a read/write preamplifier circuit that includes multiple read/write preamplifiers. Each read/write preamplifier includes a fault detecting circuit that detects when two or more of the read/write preamplifiers are concurrently selected for communicating with their associated data heads. At least one of the read/write preamplifiers includes a notifier that notifies the drive controller that two or more of the read/write preamplifiers are concurrently selected.
In one embodiment of the present invention, the notifier includes a data storage register that the drive controller can read. The data storage register includes a fault flag which is set when the fault detecting circuit detects that two or more of the read/write preamplifiers are concurrently selected for communicating with their associated data heads.
In one embodiment of the present invention, the fault detecting circuit includes a fault-detect transistor and a sensing circuit coupled to the collector of the fault-detect transistor. The fault-detect transistor drives a predetermined current when a predetermined voltage is applied to the base of the fault-detect transistor. The base of the fault-detect transistor is coupled to a signal which applies the predetermined voltage to the base if the associated read/write preamplifier is selected. The collectors of the fault-detect transistors of each of the read/write preamplifiers are electronically coupled to each other. The sensing circuit senses if the fault-detect transistors of two or more read/write preamplifiers are concurrently driving the predetermined current.
Another embodiment of the present invention is directed to a disc drive that includes at least one disc, multiple data heads, a drive controller and multiple read/write preamplifiers. The data heads transfer data to and from the discs. The read/write preamplifiers communicate with the drive controller and with at least one data head. Each read/write preamplifier includes a fault detecting circuit and a data storage register that the drive controller can read. The fault detecting circuit detects when two or more of the read/write preamplifiers are concurrently selected for communicating with their associated data heads. The data storage register includes a fault flag which is set when the fault detecting circuit detects that two or more of the read/write preamplifiers are concurrently selected for communicating with their associated data heads.
In one embodiment of a disc drive according to the present invention, the data storage register further includes a test-select flag and the hard-wired address of the read/write preamplifier. The test-select flag must be set in order to enable the fault detecting circuit. Clearing the test-select flag disables the fault detecting circuit. Additionally, the data storage register is adapted to store the address of the data head that is selected. The drive controller provides the address of the selected data head to the data storage register when the data head is selected.
Still another embodiment of the present invention is directed to a disc drive that includes a drive controller, multiple read/write preamplifiers and means for determining if two or more read/write preamplifiers are concurrently selected and for notifying the drive controller when two or more read/write preamplifiers are concurrently selected.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.
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Berger Derek J.
Davidson Dan I.
Dempster Shawn B.
Hudspeth David
Olson Jonathan E.
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