05434825 is referenced by 241 patents and cites 34 patents.

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 than the usual one bit of information. More than one bit is stored in a cell by establishing more than two distinct threshold states into which the cell is programmed. A series of pulses of increasing voltage is applied to each addressed memory cell during its programming, the state of the cell being read in between pulses. The pulses are terminated upon the addressed cell reaching its desired state or a preset maximum number of pulses has been reached. An intelligent erase algorithm prolongs the useful life of the memory cells. A series of pulses is also applied to a block of cells being erased, the state of at least a sample number of cells being read in between pulses. The erasing process is stopped when the cells being read are determined to have reached a fully erased state or one of a number of other conditions has occurred. Individual records of 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 of the 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 memory in place of magnetic disk storage devices in computer systems.

Title
Flash EEPROM system cell array with more than two storage states per memory cell
Application Number
204175
Publication Number
5434825
Application Date
September 3, 1993
Publication Date
July 18, 1995
Inventor
Eliyahou Harari
104 Auzerais Court, Los Gatos, 95030
CA, US
Agent
Majestic Parsons Siebert & Hsue
IPC
G11C 16/04
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