Multi-bit-per-cell flash memory device with non-bijective mapping
AssigneeSanDisk IL 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.
Claims11
A method of storing a plurality of input bits, comprising the steps of:
- (a) mapping the input bits to a corresponding programmed state of at least one memory cell, using a mapping that is:
- (i) into, and
- (ii) a generalized Gray mapping;
- and
- (b) programming said at least one memory cell to said corresponding programmed state.
A memory device comprising:
- (a) at least one cell;
- and
- (b) a controller operative to store a plurality of bits in said at least one cell by:
- (i) mapping the bits to a corresponding programmed state of said at least one cell, using a mapping that is:
- (A) into, and
- (B) a generalized Gray mapping, and
- (ii) programming said at least one cell to said corresponding programmed state.
A system for storing a plurality of bits, comprising:
- (a) a memory device that includes at least one cell;
- and
- (b) a processor operative:
- (i) to map the bits to a corresponding programmed state of said at least one cell, using a mapping that is:
- (A) into, and
- (B) a generalized Gray mapping, and
- (ii) to program said at least one cell to said corresponding programmed state.
A computer-readable storage medium having computer-readable code embodied in the computer-readable storage medium, the computer-readable code for storing a plurality of input bits, the computer-readable code comprising:
- (a) program code for mapping the input bits to a corresponding programmed state of at least one memory cell, using a mapping that is:
- (i) into, and
- (ii) a generalized Gray mapping;
- and
- (b) program code for programming said at least one memory cell to said corresponding programmed state.
A computer-readable storage medium having computer-readable code embodied in the computer-readable storage medium, the computer-readable code for storing N>1 bits in a memory device that includes at least one memory cell and that is configured to selectively place said at least one memory cell into M>2N programmed states, the computer-readable code comprising:
- (a) program code for selecting one of said programmed states to represent the bits according to a generalized Gray mapping;
- and
- (b) program code for 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.
Dependencies are inferred from the claim text.