Memory system and method of controlling nonvolatile memory
First Claim
1. A memory system comprising:
- a nonvolatile memory;
a soft decision value converting unit that converts a received word read from the nonvolatile memory into a received word having a soft decision value;
a list generating unit that generates a list of a plurality of test patterns for the received word having the soft decision value;
a test pattern decoding unit that detects an intermediate decoding word from the test pattern included in the list;
a Euclid distance calculating unit that calculates a Euclid distance between the intermediate decoding word detected by the test pattern decoding unit and the received word; and
a maximum likelihood decoding word selecting unit that maintains a maximum likelihood decoding word candidate,wherein, in a case where a Euclid distance of a first intermediate decoding word that is an intermediate decoding word detected by the test pattern decoding unit is shorter than a Euclid distance of the maintained maximum likelihood decoding word candidate, the maximum likelihood decoding word selecting unit updates the maintained maximum likelihood decoding word candidate by using the first intermediate decoding word and outputs the maximum likelihood decoding word candidate that is finally maintained as a soft decision output value, andthe test pattern decoding unit does not execute decoding of a test pattern having no possibility that the Euclid distance of the intermediate decoding word becomes shorter than the Euclid distance of the maximum likelihood decoding word candidate maintained by the maximum likelihood decoding word selecting unit.
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Accused Products
Abstract
According to an embodiment, a memory system includes: a test pattern decoding unit that detects an intermediate decoding word from a plurality of test patterns; a Euclid distance calculating unit that calculates a Euclid distance between the intermediate decoding word and a received word; and a maximum likelihood decoding word selecting unit that maintains a maximum likelihood decoding word candidate. In a case where a Euclid distance of the intermediate decoding word is shorter than a Euclid distance of the maximum likelihood decoding word candidate, the maximum likelihood decoding word selecting unit updates the maximum likelihood decoding word candidate by using the intermediate decoding word and the test pattern decoding unit does not execute decoding of a test pattern having no possibility that the Euclid distance of the intermediate decoding word becomes shorter than the Euclid distance of the maximum likelihood decoding word candidate.
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Citations
20 Claims
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1. A memory system comprising:
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a nonvolatile memory; a soft decision value converting unit that converts a received word read from the nonvolatile memory into a received word having a soft decision value; a list generating unit that generates a list of a plurality of test patterns for the received word having the soft decision value; a test pattern decoding unit that detects an intermediate decoding word from the test pattern included in the list; a Euclid distance calculating unit that calculates a Euclid distance between the intermediate decoding word detected by the test pattern decoding unit and the received word; and a maximum likelihood decoding word selecting unit that maintains a maximum likelihood decoding word candidate, wherein, in a case where a Euclid distance of a first intermediate decoding word that is an intermediate decoding word detected by the test pattern decoding unit is shorter than a Euclid distance of the maintained maximum likelihood decoding word candidate, the maximum likelihood decoding word selecting unit updates the maintained maximum likelihood decoding word candidate by using the first intermediate decoding word and outputs the maximum likelihood decoding word candidate that is finally maintained as a soft decision output value, and the test pattern decoding unit does not execute decoding of a test pattern having no possibility that the Euclid distance of the intermediate decoding word becomes shorter than the Euclid distance of the maximum likelihood decoding word candidate maintained by the maximum likelihood decoding word selecting unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of controlling a nonvolatile memory, the method comprising:
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reading a received word from the nonvolatile memory; converting the read received word into a received word having a soft decision value; generating a list of a plurality of test patterns for the received word having the soft decision value; detecting a first intermediate decoding word from a first test pattern included in the list; calculating a first Euclid distance between the first intermediate decoding word and the received word; maintaining the first intermediate decoding word as a maximum likelihood decoding word candidate; detecting a second intermediate decoding word from a second test pattern included in the list; calculating a second Euclid distance between the second intermediate decoding word and the received word; updating the maintained maximum likelihood decoding word candidate by using the second intermediate decoding word in a case where the second Euclid distance is shorter than the first Euclid distance; and outputting the maximum likelihood decoding word candidate that is finally maintained as a soft decision output value, wherein a test pattern having no possibility that a Euclid distance of the detected intermediate decoding word becomes shorter than the first Euclid distance is not used in the detection of the second intermediate decoding word. - View Dependent Claims (19, 20)
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Specification