Patent ID: 6788575
Filing Date: 2004-09-07
Classification: G06F,G11C

Abstract:
A nonvolatile memory comprising a memory array including a plurality of nonvolatile memory cells permitting electrical writing and erasing of information to be stored and storing information correspondingly to a threshold voltage, said nonvolatile memory performing writing and erasing in prescribed units, comprising:a replacing function to replace a group of memory cells including defective memory cells which are incapable of normal writing or erasing with a group of memory cells including no defective memory cell; a numbers of rewrites averaging function to grasp the number of data rewrites in each group of memory cells and to perform replacement of memory cell groups such that there may arise no substantial difference in the number of rewrites among a plurality of memory cell groups; and an error correcting function to detect and correct any error in data stored in said memory array, wherein first address translation information deriving from said replacing function and second address translation information deriving from said numbers of rewrites averaging function are stored in respectively prescribed areas in said memory array, and wherein said first address translation information and second address translation information concerning the same memory cell group are stored in a plurality of sets in a time series.