Abstract: A memory system includes a non-volatile memory configured to store an N-dimensional error correction code and a memory controller.

Abstract: A memory system of an embodiment includes a non-volatile memory and a memory controller. The memory controller executes a first decoding process of reading data encoded by an error correction code from the non-volatile memory and repeatedly executing bounded distance decoding on a symbol group protected by each of component codes included in N component code groups; executes a second decoding process of repeatedly executing decoding exceeding a bounded distance in units of component codes for an error symbol group determined to include an error due to a syndrome of a component code included in the N component code groups when the first decoding process fails; executes a rollback process when the first decoding process executed after the second decoding process fails; and changes a parameter used in the second decoding process and further executes the second decoding process when it is detected that the second decoding process is not progressed.

Abstract: A memory system includes a non-volatile memory configured to store an N-dimensional error correction code and a memory controller.

Abstract: According to one embodiment, a semiconductor memory includes a first memory cell array including a plurality of first memory cells; and a second memory cell array including a plurality of second memory cells. Each of threshold voltages of the first memory cells and the second memory cells is set to any of a first threshold voltage, a second threshold voltage higher than the first threshold voltage, and a third threshold voltage higher than the second threshold voltage. Data of three or more bits including a first bit, a second bit, and a third bit is stored using a combination of a threshold voltage of the first memory cell and a threshold voltage of the second memory cell.

Abstract: According to one embodiment, a semiconductor memory includes a first memory cell array including a plurality of first memory cells; and a second memory cell array including a plurality of second memory cells. Each of threshold voltages of the first memory cells and the second memory cells is set to any of a first threshold voltage, a second threshold voltage higher than the first threshold voltage, and a third threshold voltage higher than the second threshold voltage. Data of three or more bits including a first bit, a second bit, and a third bit is stored using a combination of a threshold voltage of the first memory cell and a threshold voltage of the second memory cell.

Abstract: A memory system includes a nonvolatile memory and a memory controller. The nonvolatile memory stores a multidimensional error correction code in which each of a plurality of symbol groups is encoded by both a first component code and a second component code. The memory controller reads the error correction code from the nonvolatile memory, executes a first decoding process using the first component code and the second component code, and when the first decoding process fails, executes a second decoding process on an error symbol group. The second decoding process includes a process of selecting the positions of a plurality of symbols whose values included in the error symbol group are to be inverted according to a decision rule. The decision rule includes a rule for cyclically shifting a position selected for the second decoding process at to decide the position for the second decoding process at the next time.

Abstract: According to one embodiment, a memory system includes a non-volatile memory, a memory interface that reads data recorded in the non-volatile memory as a received value, a converting unit that converts the received value to first likelihood information by using a first conversion table, a decoder that decodes the first likelihood information, a control unit that outputs an estimated value with respect to the received value, which is a decoding result obtained by the decoding, when decoding by the decoder has succeeded, and a generating unit that generates a second conversion table based on a decoding result obtained by the decoding, when decoding of the first likelihood information by the decoder has failed. When the generating unit generates the second conversion table, the converting unit converts the received value to the second likelihood information by using the second conversion table, and the decoder decodes the second likelihood information.

Abstract: According to one embodiment, a memory system includes a nonvolatile memory, and a memory controller. Each of first storage regions of each of the nonvolatile memory includes a plurality of second storage regions. Each of pieces of first data includes pieces of second data as storage target data. Third data includes pieces of the second data that are selected one by one from each of the pieces of first data. The memory controller executes first decoding of decoding each of the pieces of first data on the basis of a first error correcting code generated by using the first data, and executes second decoding of decoding the third data including a bit of which reliability, which relates to each bit in each of the second storage regions that fail in the first decoding, is less than reliability of other bits on the basis of a second error correcting code.

Abstract: According to one embodiment, a memory system includes a non-volatile memory, a memory interface that reads data recorded in the non-volatile memory as a received value, a converting unit that converts the received value to first likelihood information by using a first conversion table, a decoder that decodes the first likelihood information, a control unit that outputs an estimated value with respect to the received value, which is a decoding result obtained by the decoding, when decoding by the decoder has succeeded, and a generating unit that generates a second conversion table based on a decoding result obtained by the decoding, when decoding of the first likelihood information by the decoder has failed. When the generating unit generates the second conversion table, the converting unit converts the received value to the second likelihood information by using the second conversion table, and the decoder decodes the second likelihood information.

Abstract: A semiconductor memory device according to an embodiment includes first memory cells, second memory cells, and a controller. A threshold voltage of each of the first memory cells and the second memory cells is included in one of first through sixteenth state. 8-bit data that includes a first through eighth bit is stored using a combination of a threshold voltage of the first memory cell and a threshold voltage of the second memory cell. The controller is configured to: apply in parallel a plurality of types of read voltages to each of the first memory cells and the second memory cells and externally output data confirmed based on first data read from the first memory cells and second data read from the second memory cells.

Abstract: A memory system includes a nonvolatile memory and a memory controller. The nonvolatile memory has data encoded with an error correction code stored therein. The memory controller reads data from the nonvolatile memory, calculates likelihood information from the read data and an LLR table for calculating the likelihood information, determines a parameter for a decoding process of the read data based on the likelihood information, executes the decoding process based on the determined parameter, and outputs a decoding result obtained by the decoding process.

Abstract: A memory system includes a nonvolatile memory and a memory controller. The nonvolatile memory stores a multidimensional error correction code in which each of a plurality of symbol groups is encoded by both a first component code and a second component code. The memory controller reads the error correction code from the nonvolatile memory, executes a first decoding process using the first component code and the second component code, and when the first decoding process fails, executes a second decoding process on an error symbol group. The second decoding process includes a process of selecting the positions of a plurality of symbols whose values included in the error symbol group are to be inverted according to a decision rule. The decision rule includes a rule for cyclically shifting a position selected for the second decoding process at to decide the position for the second decoding process at the next time.

Abstract: A semiconductor memory includes a first memory cell configured to be set with a first threshold voltage, the first threshold voltage being one of different threshold voltage levels, a second memory cell configured to be set with a second threshold voltage, the second threshold voltage being one of different threshold voltage levels, a first word line coupled to the first memory cell, a second word line coupled to the second memory cell, and a controller configured to read data of one of different bits based on a combination of the first threshold voltage of the first memory cell and the second threshold voltage of the second memory cell.

Abstract: A semiconductor memory device includes a plurality of detecting code generators configured to generate a plurality of detecting codes to detect errors in a plurality of data items, respectively, a plurality of first correcting code generators configured to generate a plurality of first correcting codes to correct errors in a plurality of first data blocks, respectively, each of the first data blocks containing one of the data items and a corresponding detecting code, a second correcting code generators configured to generate a second correcting code to correct errors in a second data block, the second data block containing the first data blocks, and a semiconductor memory configured to nonvolatilely store the second data block, the first correcting codes, and the second correcting code.

Abstract: A semiconductor memory device includes a plurality of detecting code generators configured to generate a plurality of detecting codes to detect errors in a plurality of data items, respectively, a plurality of first correcting code generators configured to generate a plurality of first correcting codes to correct errors in a plurality of first data blocks, respectively, each of the first data blocks containing one of the data items and a corresponding detecting code, a second correcting code generators configured to generate a second correcting code to correct errors in a second data block, the second data block containing the first data blocks, and a semiconductor memory configured to nonvolatilely store the second data block, the first correcting codes, and the second correcting code.

Abstract: In general, according to an embodiment, a memory system includes a memory device including a memory cell; and a controller. The controller is configured to: receive first data from the memory cell in a first data reading; receive second data from the memory cell in a second data reading that is different from the first data reading; convert a first value that is based on the first data and the second data, to a second value in accordance with a first relationship; and convert the first value to a third value in accordance with a second relationship that is different from the first relationship.

Abstract: A memory system includes a nonvolatile memory and a memory controller that encodes first XOR data generated by performing an exclusive OR operation on pieces of user data, wherein a value of each bit of the XOR data is generated by performing an exclusive OR operation on values of bits that are at one of a plurality of bit positions of a piece of user data, generates codewords by encoding the plurality of pieces of user data and the generated XOR data, respectively, and stores the codewords in the nonvolatile memory. The memory controller also performs a read operation by reading the codewords from the nonvolatile memory and decoding them. When the decoding of two or more of the codewords fails, the memory controller generates second XOR data, and corrects the value of one of the bits corresponding to a codeword whose decoding failed, based on the second XOR data.

Abstract: A semiconductor memory according to an embodiment includes first and second memory cells, first and second memory cell arrays, first and second word lines, and controller. The first and second memory cell array include the first and second memory cells, respectively. The first and second word lines are coupled to the first and second memory cells, respectively. Data of six or more bits including a first bit, a second bit, a third bit, a fourth bit, a fifth bit, and a sixth bit is stored with the use of a combination of a threshold voltage of the first memory cell and a threshold voltage of the second memory cell.

Abstract: A memory system includes a nonvolatile memory and a memory controller that encodes first XOR data generated by performing an exclusive OR operation on pieces of user data, wherein a value of each bit of the XOR data is generated by performing an exclusive OR operation on values of bits that are at one of a plurality of bit positions of a piece of user data, generates codewords by encoding the plurality of pieces of user data and the generated XOR data, respectively, and stores the codewords in the nonvolatile memory. The memory controller also performs a read operation by reading the codewords from the nonvolatile memory and decoding them. When the decoding of two or more of the codewords fails, the memory controller generates second XOR data, and corrects the value of one of the bits corresponding to a codeword whose decoding failed, based on the second XOR data.

Abstract: In general, according to an embodiment, a memory system includes a memory device including a memory cell; and a controller. The controller is configured to: receive first data from the memory cell in a first data reading; receive second data from the memory cell in a second data reading that is different from the first data reading; convert a first value that is based on the first data and the second data, to a second value in accordance with a first relationship; and convert the first value to a third value in accordance with a second relationship that is different from the first relationship.