Abstract: According to one embodiment, a memory system includes a nonvolatile memory and a memory controller. The nonvolatile memory includes blocks each including memory cells. The memory controller is configured to control access to the nonvolatile memory. The memory controller is configured to: set a first block, among the plurality of blocks, to be written in a first mode, the first mode being a mode in which data of a first number of bits is written into the memory cell, and set a plurality of second blocks, among the plurality of blocks, to be written in a second mode, the second mode being a mode in which data of a second number of bits is written into the memory cell, the second number being larger than the first number; acquire access information related to the second blocks; and change a writing mode of the first block which has been set in the first mode to the second mode when a first condition of the second blocks based on the access information is satisfied.

Abstract: A memory system according to an embodiment includes a nonvolatile memory and a memory controller. The nonvolatile memory includes a plurality of memory cells. The memory controller is configured to control the nonvolatile memory. In read operation for the memory cells, the memory controller is configured to: perform tracking including a plurality of reads in which a read voltage is shifted; determine a hard bit read voltage based on results of the tracking; calculate a soft bit read voltage based on the determined hard bit read voltage; perform soft bit read using the calculated soft bit read voltage; and perform a soft bit decoding process using a result of the soft bit read and a log-likelihood ratio table associated with the calculated soft bit read voltage.

Abstract: According to one embodiment, a memory system includes a nonvolatile semiconductor memory, and a controller. The semiconductor memory includes a memory cell, and a write circuit configured to write data to the memory cell by applying a program voltage to the memory cell and comparing a threshold voltage of the memory cell with a first reference voltage corresponding to the write data. The write circuit is configured to execute a first programming operation to obtain a value of a write parameter by comparing the threshold voltage with a second reference voltage different from the first reference voltage.

Abstract: A memory system includes a non-volatile memory having a plurality of memory cells and a controller. The controller is configured to switch a mode for controlling an access operation to the non-volatile memory from a first mode to a second mode, in response to receiving from a host, a first command for instructing the controller to switch the mode from the first mode to the second mode. The access operation controlled according to the second mode improves data retention relative to the access operation controlled according to the first mode.

Abstract: According to one embodiment, a memory system includes a nonvolatile memory and a controller electrically connected to the nonvolatile memory. The controller selects a write mode from a first mode in which data having N bits is written per one memory cell and a second mode in which data having M bits is written per one memory cell. N is equal to or larger than one. M is larger than N. The controller writes data into the nonvolatile memory in the selected write mode. The controller selects either the first mode or the second mode at least based on a total number of logical addresses mapped in a physical address space of the nonvolatile memory.

Abstract: A memory system includes a non-volatile memory having a plurality of memory cells and a controller. The controller is configured to switch a mode for controlling an access operation to the non-volatile memory from a first mode to a second mode, in response to receiving from a host, a first command for instructing the controller to switch the mode from the first mode to the second mode. The access operation controlled according to the second mode improves data retention relative to the access operation controlled according to the first mode.

Abstract: According to one embodiment, a memory system includes a semiconductor memory and a controller. The semiconductor memory includes blocks each containing memory cells. The controller is configured to instruct the semiconductor memory to execute a first operation and a second operation. In the first operation and the second operation, the semiconductor memory selects at least one of the blocks, and applies at least one voltage to all memory cells contained in said selected blocks. A number of blocks to which said voltage is applied per unit time in the second operation is larger than that in the first operation.

Abstract: According to one embodiment, a nonvolatile memory includes a plurality of memory areas and controller circuit including an error correction code encoder. The error correction code encoder encodes a first data to generate a first parity in a first operation and encodes a second data to generate a second parity in a second operation. The controller circuit writes the first data and the first parity into a first memory area among the plurality of memory areas and writes the second data and the second parity into a second memory area among the plurality of memory areas. The size of the second data is smaller than the size of the first data and the size of the second parity is equal to the size of the first parity.

Abstract: According to one embodiment, a memory system includes a nonvolatile memory and a controller electrically connected to the nonvolatile memory. The controller selects a write mode from a first mode in which data having N bits is written per one memory cell and a second mode in which data having M bits is written per one memory cell. N is equal to or larger than one. M is larger than N. The controller writes data into the nonvolatile memory in the selected write mode. The controller selects either the first mode or the second mode at least based on a total number of logical addresses mapped in a physical address space of the nonvolatile memory.

Abstract: According to one embodiment, a memory system includes a non-volatile memory and a memory controller. The non-volatile memory includes a plurality of groups, each including a plurality of memory cells. The memory controller is configured to determine whether to execute a refresh process for a first group based on whether a first temperature in a write process for the first group and a second temperature after the write process for the first group satisfy a first condition.

Abstract: According to one embodiment, a memory system includes a memory controller and a nonvolatile memory with multiple planes each provided with multiple word lines, memory cell groups, dummy word lines, and dummy memory cell groups. The memory controller writes data to a memory cell group connected to a corresponding word line of any of the planes, such that a plane to which k-th data are to be written is different from a plane to which (k+m?1)-th data are to be written, and writes the parities to any of the dummy memory cell groups. The combinations of the data used for generating the different parities are different from each other.

Abstract: According to one embodiment, a memory system includes a semiconductor memory and a controller. The semiconductor memory includes blocks each containing memory cells. The controller is configured to instruct the semiconductor memory to execute a first operation and a second operation. In the first operation and the second operation, the semiconductor memory selects at least one of the blocks, and applies at least one voltage to all memory cells contained in said selected blocks. A number of blocks to which said voltage is applied per unit time in the second operation is larger than that in the first operation.

Abstract: According to one embodiment, a memory system includes a nonvolatile semiconductor memory, and a controller. The semiconductor memory includes a memory cell, and a write circuit configured to write data to the memory cell by applying a program voltage to the memory cell and comparing a threshold voltage of the memory cell with a first reference voltage corresponding to the write data. The write circuit is configured to execute a first programming operation to obtain a value of a write parameter by comparing the threshold voltage with a second reference voltage different from the first reference voltage.

Abstract: According to one embodiment, a nonvolatile memory includes a plurality of memory areas and controller circuit including an error correction code encoder. The error correction code encoder encodes a first data to generate a first parity in a first operation and encodes a second data to generate a second parity in a second operation. The controller circuit writes the first data and the first parity into a first memory area among the plurality of memory areas and writes the second data and the second parity into a second memory area among the plurality of memory areas. The size of the second data is smaller than the size of the first data and the size of the second parity is equal to the size of the first parity.

Abstract: According to one embodiment, a memory system includes a nonvolatile semiconductor memory, and a controller. The semiconductor memory includes a memory cell, and a write circuit configured to write data to the memory cell by applying a program voltage to the memory cell and comparing a threshold voltage of the memory cell with a first reference voltage corresponding to the write data. The write circuit is configured to execute a first programming operation to obtain a value of a write parameter by comparing the threshold voltage with a second reference voltage different from the first reference voltage.

Abstract: A memory system includes a non-volatile memory chip that includes a memory cell array, and a memory controller. The memory controller is configured to perform a read operation on the non-volatile memory chip by instructing the non-volatile memory chip to perform a sensing operation to read data stored in the memory cell array, estimating a time when the read data becomes ready to be transferred from the non-volatile memory chip to the memory controller, and instructing the non-volatile memory chip, after the estimated time, to perform a transfer operation to transfer the read data to the memory controller.

Abstract: A memory system includes a non-volatile memory having a plurality of memory cells and a controller. The controller is configured to switch a mode for controlling an access operation to the non-volatile memory from a first mode to a second mode, in response to receiving from a host, a first command for instructing the controller to switch the mode from the first mode to the second mode. The access operation controlled according to the second mode improves data retention relative to the access operation controlled according to the first mode.

Abstract: A memory system according to an embodiment includes a nonvolatile memory and a memory controller. The nonvolatile memory includes a plurality of memory cells. The memory controller is configured to control the nonvolatile memory. In read operation for the memory cells, the memory controller is configured to: perform tracking including a plurality of reads in which a read voltage is shifted; determine a hard bit read voltage based on results of the tracking; calculate a soft bit read voltage based on the determined hard bit read voltage; perform soft bit read using the calculated soft bit read voltage; and perform a soft bit decoding process using a result of the soft bit read and a log-likelihood ratio table associated with the calculated soft bit read voltage.

Abstract: A memory system includes a non-volatile memory chip that includes a memory cell array, and a memory controller. The memory controller is configured to perform a read operation on the non-volatile memory chip by instructing the non-volatile memory chip to perform a sensing operation to read data stored in the memory cell array, estimating a time when the read data becomes ready to be transferred from the non-volatile memory chip to the memory controller, and instructing the non-volatile memory chip, after the estimated time, to perform a transfer operation to transfer the read data to the memory controller.

Abstract: A memory system includes a non-volatile memory having a plurality of memory cells and a controller. The controller is configured to switch a mode for controlling an access operation to the non-volatile memory from a first mode to a second mode, in response to receiving from a host, a first command for instructing the controller to switch the mode from the first mode to the second mode. The access operation controlled according to the second mode improves data retention relative to the access operation controlled according to the first mode.