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

To: Art Bechhoefer who wrote (14715)	9/11/2000 10:00:48 AM
From: NHP	Read Replies (2) \| Respond to of 60323

Cirrus Patents Filed in 1993 Art and thread, FYI United States Patent 5,485,595 Assar , et al. January 16, 1996 Flash memory mass storage architecture incorporating wear leveling technique without using cam cells Abstract A semiconductor mass storage device can be substituted for a rotating hard disk. The device avoid an erase cycle each time information stored in the mass storage is changed. Erase cycles are avoided by programming an altered data file into an empty mass storage block rather than over itself as a hard disk would. Periodically, the mass storage will need to be cleaned up. Secondly, a circuit and method are provided for evenly using all blocks in the mass storage. These advantages are achieved through the use of several flags, a map to correlate a logical address of a block to a physical address of that block and a count register for each block. In particular, flags are provided for defective blocks, used blocks, old versions of a block, a count to determine the number of times a block has been erased and written and an erase inhibit flag. Reading is performed by providing the logical block address to the memory storage. The system sequentially compares the stored logical block addresses until it finds a match. That data file is then coupled to the system. Inventors: Assar; Mahmud (Morgan Hill, CA); Estakhri; Petro (Pleasonton, CA); Nemazie; Siamack (San Jose, CA); Mozaffari; Mahmood (San Jose, CA) Assignee: Cirrus Logic, Inc. (Fremont, CA) Appl. No.: 31495 Filed: October 4, 1993 ------------------------------------------------------------ United States Patent 5,479,638 Assar , et al. December 26, 1995 Flash memory mass storage architecture incorporation wear leveling technique Abstract A semiconductor mass storage device can be substituted for a rotating hard disk. The device avoids an erase cycle each time information stored in the mass storage is changed. (The erase cycle is understood to include, fully programming the block to be erased, and then erasing the block.) Erase cycles are avoided by programming an altered data file into an empty mass storage block rather than over itself as a hard disk would. Periodically, the mass storage will need to be cleaned up. Secondly, a circuit for evenly using all blocks in the mass storage is provided. These advantages are achieved through the use of several flags, a map to directly correlate a logical address of a block to a physical address of that block and a count register for each block. In particular, flags are provided for defective blocks, used blocks, old version of a block, a count to determine the number of times a block has been erased and written and erase inhibit. Inventors: Assar; Mahmud (Morgan Hill, CA); Nemazie; Siamack (San Jose, CA); Estakhri; Petro (Pleasonton, CA) Assignee: Cirrus Logic, Inc. (Palo Alto, CA) Appl. No.: 037893 Filed: March 26, 1993 --------------------------------- NHP