AVOIDING ERRORS IN A FLASH MEMORY BY USING SUBSTITUTION TRANSFORMATIONS

摘要

Memory circuitry, or a memory device controller, or a host of a memory device, store an input string of M N-tuples of bits by selecting a substitution transformation in accordance with the input string and by applying the transformation to the input string to provide a transformed string of M N-tuples of bits. M or more memory cells are programmed to represent the transformed string and preferably also to represent a key of the transformation. Alternatively, the circuitry selectively programs each of M or more cells to a respective one of 2N states. The circuitry or the controller selects a mapping that maps the binary numbers in [0,2N-1] into respective states in accordance with the input string and the circuitry uses the mapping to program M cells to represent the input string. Preferably, a key of the mapping is stored in the memory in association with the M cells.