Cirrus Logic Inc.

Sensor-Tech Limited

William L Witt

Neal Glover

Christopher P Zook

John J Schadegg

Richard T Behrens

Marcus L Caldwell

Laura Droege Shellhamer

Gary Ross Mitchell

Gerald Patrick Sweetman

A disc drive storage system having a plurality of data tracks and data sectors within each track, wherein each track further comprises a redundancy sector for reconstructing a data sector unrecoverable at the sector level. The latency of the storage system is minimized by generating track level redundancy data over the write range of data sectors and storing the 'write' redundancy to the redundancy sector. Then during idle time of the storage system, the track level redundancy is regenerated for the entire track. If an unrecoverable data sector is encountered during the idle time redundancy regeneration, and the unrecoverable data sector is within the write range of the previous write operation, then it is reconstructed using the track level redundancy data stored in the redundancy sector.

Write verify method for correcting unrecoverable sectors in a disc

A defect management system is disclosed for disc storage systems which avoids the access latency associated with conventional linear replacement techniques by dispersing spare segments throughout each track at a regular interval and buffering sectors inbetween a defective sector and the corresponding spare segment during read and write operations. In one embodiment, a spare segment is an entire sector which replaces a defective data sector; and in an alternative embodiment, a spare segment stores only the defective portion of a data sector which is more efficient, but also more complicated in implementation. In both embodiments, the defect management system comprises a defect locator for locating a defective segment within a data sector. Once located, the defect management system maps the defective sector (or the defective portion thereof) to the nearest available spare segment. Then when accessing the track that comprises the defective sector, the data sectors between the defective segment and corresponding spare segment are buffered in a data buffer, and an area in the data buffer is reserved for storing the data associated with the spare segment. In this manner, data can be written to and read from the track in a contiguous sequence without requiring an extra revolution of latency as in the conventional linear replacement defect mapping techniques.

Disc storage system with spare sectors dispersed at a regular interval

A disc storage system comprising a sector level ECS for correcting errors within a sector during readback, and a track level ECS for correcting a sector that becomes unrecoverable at the sector level either because the number of hard errors exceeds the error correction capability of the sector redundancy, or because the sector is unreadable due, for instance, to an inability to synchronize to the sector data. A data buffer stores the data sectors, and a redundancy buffer stores the track level redundancy data. If during a read operation a data sector is determined to be unrecoverable using the sector level redundancy, the storage system corrects the unrecoverable sector using the track level redundancy.

Sector and track level error correction system for disc storage systems

In a disc drive storage system employing a track level redundancy sector for reconstructing a data sector unrecoverable at the sector level, the latency of the storage system is minimized by performing a write operation according to the following steps:

Method for correcting unrecoverable sectors using track level redundancy

The present invention is a carbon monoxide or other toxic gas detector. The detector of the present invention detects the presence of carbon monoxide in an air sample by measuring the time required for the sensor circuitry to charge. Such a measurement technique eliminates the inaccuracies inherent in prior art detectors which measure the resistance of the sensor circuitry upon exposure to carbon monoxide. The detector of the present invention is controlled by a microprocessor which enables the detector to retain in memory air sample readings of carbon monoxide or other toxic gas. If the detector registers four consecutive readings which indicate the presence of carbon monoxide in an air sample in a concentration greater than or equal to about 100 ppm, then the alarm of the detector will be triggered, thereby alerting the user to a dangerous concentration of carbon monoxide gas in the air. Such a detection cycle enables the detector to detect not only high level, lethal concentrations of carbon monoxide in the air, but also, chronic, low level harmful concentrations of carbon monoxide in the air.

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Broomfield, CO, United States of America

William L Witt