Patent ID: 8321625
Filing Date: 2012-11-27
Classification: G06F,G11C

Abstract:
1. A system for determining thresholds useful for converting cell physical levels into cell logical values in an array of memory cells storing physical levels which diminish over time, the system comprising: deterioration determining apparatus determining extent of deterioration of the physical levels and determining thresholds accordingly for at least an individual cell in said array; and reading circuitry operative to read said individual cell including reading a physical level in said cell and converting said physical level into a logical value using said thresholds, wherein said deterioration determining apparatus is operative to store predefined physical levels rather than data-determined physical levels in each of a plurality of cells and to compute extent of deterioration by determining deterioration of said predefined physical levels wherein said plurality of cells comprises a number of cells selected to as to achieve a level of reading errors which does not exceed a predetermined acceptable level; wherein said reading comprises using error correction code to eliminate errors and wherein said predetermined acceptable level comprises a predetermined maximum proportion of pages containing so many errors as to be uncorrectable by said error correction code.