Multi-bit-per-cell flash memory device with non-bijective mapping

摘要

To store input data in a plurality of memory cells, a mapping function of bit sequences to physical parameter states of the cells is provided. The cells are programmed, in accordance with the mapping function, to store the input data, in a way that would store uniformly distributed data with a programming state distribution other than any native state distribution of the mapping function. To store input data in a single memory cell, a mapping function of bit sequences to states of a physical parameter of the cell, such that if uniformly distributed data were stored in a plurality of such memory cells then the states of the physical parameter of the cells would be distributed non-uniformly, is provided. The memory cell is programmed to store the input data in accordance with the mapping function.

主权项

1. A method of storing input data in a plurality of memory cells, comprising:
(a) providing a mapping function of bit sequences to states of a physical parameter of the cells; (b) programming the plurality of memory cells, in accordance with the mapping function, to store the input data, in a way that stores uniformly distributed data with a programming state distribution other than any native state distribution of the mapping function; and (c) determining the programming state distribution by at least selecting a target state distribution, and devising a transformation so that the programming state distribution approximates the target state distribution within a predetermined tolerance.