Flash EEPROM memory systems and methods of using t

专利名称：Flash EEPROM memory systems and

methods of using them

发明人：Eliyahou Harari申请号：US08/9941申请日：19971229公开号：US058315A公开日：19981110

摘要：A memory system made up of electrically programmable read only memory(EPROM) or flash electrically erasable and programmable read only memory (EEPROM)cells. An intelligent programming technique allows each memory cell to store more thanthe usual one bit of information. More than one bit is stored in a cell by establishingmore than two distinct threshold states into which the cell is programmed. A series ofpulses of increasing voltage is applied to each addressed memory cell during itsprogramming, the state of the cell being read in between pulses. The pulses areterminated upon the addressed cell reaching its desired state or a preset maximumnumber of pulses has been reached. An intelligent erase algorithm prolongs the usefullife of the memory cells. A series of pulses is also applied to a block of cells beingerased, the state of at least a sample number of cells being read in between pulses. Theerasing process is stopped when the cells being read are determined to have reached afully erased state or one of a number of other conditions has occurred. Individual recordsof the number of erase cycles experienced by blocks of flash EEPROM cells are kept,preferable as part of the blocks themselves, in order to maintain an endurance history ofthe cells within the blocks. Use of these various features provides a memory having a very

high storage density and a long life, making it particularly useful as a solid state memoryin place of magnetic disk storage devices in computer systems.

申请人：HARARI; ELIYAHOU

代理机构：Majestic, Parsons, Siebert & Hsue

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