Multi-bit-per-cell flash memory device with non-bijective mapping
AssigneeRamot at Tel-Aviv University Ltd.
InventorsSimon Litsyn, Eran Sharon, Idan Alrod
Life of this patent
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Abstract
To store a plurality of input bits, the bits are mapped to a corresponding programmed state of one or more memory cells and the cell(s) is/are programmed to that corresponding programmed state. The mapping may be many-to-one or may be an “into” generalized Gray mapping. The cell(s) is/are read to provide a read state value that is transformed into a plurality of output bits, for example by maximum likelihood decoding or by mapping the read state value into a plurality of soft bits and then decoding the soft bits.
Claims3
A method of storing N>1 bits, comprising the steps of:
- (a) configuring a memory device that includes at least one memory cell to selectively place said at least one memory cell into M>2N programmed states;
- (b) selecting one of said programmed states to represent the bits according to a generalized Gray mapping;
- and
- (c) programming said at least one memory cell to said selected programmed state;
- wherein at least one of said programmed states is excluded from said selecting.
A memory device, for storing N>1 bits, comprising:
- (a) at least one cell;
- and
- (b) a controller operative:
- (i) to selectively place at least one said cell into M>2N programmed states,
- (ii) to select one of said programmed states to represent the bits according to a generalized Gray mapping, and
- (iii) to program said at least one cell to said selected programming state;
- wherein at least one of said programmed state is excluded from said selecting.
A system for storing N>1 bits, comprising:
- (a) a memory device that includes at least one cell;
- and
- (b) a processor operative:
- (i) to selectively place at least one said cell into we M>2N programmed states,
- (ii) to select one of said programmed states to represent the bits according to a generalized Gray mapping, and
- (iii) to program said at least one cell to said selected programming state;
- wherein at least one of said programmed state is excluded from said selecting.
Dependencies are inferred from the claim text.