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Technology Stocks : WDC/Sandisk Corporation -- Ignore unavailable to you. Want to Upgrade?

To: Ron C who wrote (4944)	3/4/1999 12:57:00 AM
From: Diamondhead	Respond to of 60323

Latest patent: PATENT No: 5877986 ISSUE DATE: Mar-02-1999 Multi-state Flash EEprom system on a card that includes defective cell substitution ASSIGNEE: SanDisk Corporation Sunnyvale, CA INVENTOR: Harari; Eliyahou Los Gatos, CA Norman; Robert D. San Jose, CA Mehrotra; Sanjay Milpitas, CA OTHER DETAILS: Legal Rep: Majestic, Parsons, Siebert Hsue Application Date: Dec-29-1997 Application Number: 999472 Primary Examiner: Nelms; David ABSTRACT: A system of Flash EEprom memory chips with controlling circuits serves as non-volatile memory such as that provided by magnetic disk drives. Improvements include selective multiple sector erase, in which any combinations of Flash sectors may be erased together. Selective sectors among the selected combination may also be de-selected during the erase operation. Another improvement is the ability to remap and replace defective cells with substitute cells. The remapping is performed automatically as soon as a defective cell is detected. When the number of defects in a Flash sector becomes large, the whole sector is remapped. Yet another improvement is the use of a write cache to reduce the number of writes to the Flash EEprom memory, thereby minimizing the stress to the device from undergoing too many write/erase cycling.