Procedure for storing and reading data in a non-volatile multi-level storage with a non-trivial number of levels and associated circuit architecture

摘要

According to the multilevel programming method, each memory location (10a, 10b) can be programmed at a non-binary number of levels. An integer number of bits, for example 5, is stored in two adjacent memory locations (10a, 10b). To this end, the bits to be stored in the two locations are divided into two sets, wherein the first set defines a binary number of levels higher than the non-binary number of levels. During programming, if the first set of bits to be written corresponds to a number smaller than the non-binary number of levels, the first set of bits is written in the first location and the second set of bits is written in the second location (33, 34); if, instead, it is greater than the non-binary number of levels, the first set of bits is written in the second location and the second set of bits is written in the first location (35, 36). The bits of the first set written in the second location (10b) are stored in different levels with respect to the bits of the second set. Consequently, during reading, first it is verified(42) whether the levels reserved to the first set have been written, and the bits read in the two locations are appropriately associated to the two sets of bits. IMAGE IMAGE