Soft-input soft-output decoder for nonvolatile memory
First Claim
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1. A nonvolatile memory system comprising:
- a memory array including a plurality of cells for storing a modulated plurality of data bits and a plurality of parity bits that are calculated from the plurality of data bits according to an encoding scheme;
a demodulator for reading the plurality of cells and deriving raw likelihood values corresponding to the plurality of data bits and the plurality of parity bits, wherein the demodulator is further operable to read each memory cell using a predetermined pattern of read operations, the pattern having at least one area of higher density and one area of lower density; and
a decoder for receiving the raw likelihood values and calculating output likelihood values therefrom using a decoding scheme that corresponds to the encoding scheme.
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Abstract
In a nonvolatile memory system, data is read from a memory array and used to obtain likelihood values, which are then provided to a soft-input soft-output decoder. The soft-input soft-output decoder calculates output likelihood values from input likelihood values and from parity data that was previously added according to an encoding scheme.
167 Citations
19 Claims
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1. A nonvolatile memory system comprising:
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a memory array including a plurality of cells for storing a modulated plurality of data bits and a plurality of parity bits that are calculated from the plurality of data bits according to an encoding scheme; a demodulator for reading the plurality of cells and deriving raw likelihood values corresponding to the plurality of data bits and the plurality of parity bits, wherein the demodulator is further operable to read each memory cell using a predetermined pattern of read operations, the pattern having at least one area of higher density and one area of lower density; and a decoder for receiving the raw likelihood values and calculating output likelihood values therefrom using a decoding scheme that corresponds to the encoding scheme. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A nonvolatile memory system comprising:
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a nonvolatile memory array for storing two or more bits in an individual memory cell; and a demodulator for deriving an individual likelihood value for each of the two or more bits stored in the individual memory cell, wherein the demodulator is operable to read the individual memory cell using a predetermined pattern of read operations, the pattern having at least one area of higher density and one area of lower density. - View Dependent Claims (10, 11, 12, 13)
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14. A nonvolatile memory system comprising:
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an array of nonvolatile memory cells for individually programming to one of two or more threshold voltage ranges that represent two or more states; and a demodulator for resolving an individual cell threshold voltage to an identified one of the two or more threshold voltage ranges and further resolving the individual cell threshold voltage within the identified threshold voltage range by providing a higher density of read operations for a first portion of the identified threshold voltage range than at for a second portion of the identified threshold voltage range, the demodulator being further configured for deriving likelihood values from the read operations for the first and second portions. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification