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: 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 non-volatile memory and volatile memory. A controller encodes a first unit size data portion to be written into the non-volatile memory and generates a first error correction code for the data portion, then writes the data portion into the non-volatile memory. The controller also stores the first error correction code in the volatile memory. When non-volatilization of an error correction code protect the data portion is requested, the controller encodes the data portion to generate a second error correction code for the data portion, and then writes the second error correction code into the non-volatile memory. The second error correction code is smaller in size than the first error correction code.

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: A memory system includes a memory device having a memory cell array, and a controller. The memory cell array includes a plurality of first units and at least one second unit. The second unit includes the plurality of first units. The controller counts a first number of times of read operation for each of the plurality of first units, and, in response to the first number of times for one first unit among the plurality of first units reaching a first value, updates a second number of times for the second unit that includes the one first unit. In response to the second number of times reaching a second value, the controller determines whether to rewrite data stored in at least one of the first units included in the second unit.

Abstract: According to one embodiment, the semiconductor memory medium includes a first memory cell, a first word line coupled to the first memory cell, and a row decoder coupled to the first word line. A write operation is executed multiple times on the first memory cell within a first period from after an execution of an erase operation to an execution of a next erase operation. The write operation includes at least one of program loops each including a program operation and a verify operation. In the verify operation, the row decoder applies a verify voltage to the first word line. The verify voltage is set in accordance with a number of executed write operations on the first memory cell within the first period.

Abstract: A memory system includes a non-volatile memory and a controller that includes a toggle encoder configured to encode first data having a first bit length and a first number of toggles, into second data having a second bit length longer than the first bit length and a second number of toggles smaller than the first number of toggles, and transmit the second data to the non-volatile memory. The memory system may further include a toggle decoder configured to decode third data received from the non-volatile memory into fourth data, the third data having the second bit length and the second number of toggles and the fourth data having the first bit length and the first number of toggles.

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 nonvolatile memory, a random access memory and a controller. When writing n?1 data portions of a first unit that are included in n?1 error correction code frames of a first size, respectively, in the nonvolatile memory, the controller generates a second error correction code that constitutes an error correction code frame of a second size together with the n?1 data portions of the first unit and a second data portion to be written into the nonvolatile memory by encoding the n?1 data portions of the first unit and the second data portion, and writes the second data portion and the second error correction code into the nonvolatile memory.

Abstract: A memory system comprises a nonvolatile memory having a plurality of memory cells and a memory controller for controlling the nonvolatile memory. The plurality of memory cells is divided into different groups, and each group is assigned a threshold read count value from a predetermined range of read count values. The memory controller includes a counter which tracks a read count for each group, a determination circuit configured to compare the read count for each group tracked by the counter to the assigned threshold read count value for the group, and a nonvolatile memory read/write circuit configured to read data from the group when the determination circuit indicates the read count for the group has reached the assigned threshold read count value.

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: A memory system includes a memory device having a memory cell array, and a controller. The memory cell array includes a plurality of first units and at least one second unit. The second unit includes the plurality of first units. The controller counts a first number of times of read operation for each of the plurality of first units, and, in response to the first number of times for one first unit among the plurality of first units reaching a first value, updates a second number of times for the second unit that includes the one first unit. In response to the second number of times reaching a second value, the controller determines whether to rewrite data stored in at least one of the first units included in the second unit.

Abstract: According to one embodiment, the semiconductor memory medium includes a first memory cell, a first word line coupled to the first memory cell, and a row decoder coupled to the first word line. A write operation is executed multiple times on the first memory cell within a first period from after an execution of an erase operation to an execution of a next erase operation. The write operation includes at least one of program loops each including a program operation and a verify operation. In the verify operation, the row decoder applies a verify voltage to the first word line. The verify voltage is set in accordance with a number of executed write operations on the first memory cell within the first period.

Abstract: According to one embodiment, the semiconductor memory medium includes a first memory cell, a first word line coupled to the first memory cell, and a row decoder coupled to the first word line. A write operation is executed multiple times on the first memory cell within a first period from after an execution of an erase operation to an execution of a next erase operation. The write operation includes at least one of program loops each including a program operation and a verify operation. In the verify operation, the row decoder applies a verify voltage to the first word line. The verify voltage is set in accordance with a number of executed write operations on the first memory cell within the first period.

Abstract: According to one embodiment, a memory system includes non-volatile memory and volatile memory. A controller encodes a first unit size data portion to be written into the non-volatile memory and generates a first error correction code for the data portion, then writes the data portion into the non-volatile memory. The controller also stores the first error correction code in the volatile memory. When non-volatilization of an error correction code protect the data portion is requested, the controller encodes the data portion to generate a second error correction code for the data portion, and then writes the second error correction code into the non-volatile memory. The second error correction code is smaller in size than the first error correction code.

Abstract: According to one embodiment, there is provided a memory system including a non-volatile memory, and a controller. The controller selects one read method from a plurality of read methods with different time required to perform a read operation on the non-volatile memory and issues a first read command according to the selected one read method to the non-volatile memory.

Abstract: According to one embodiment, a memory system includes a nonvolatile memory, a random access memory and a controller. When writing n?1 data portions of a first unit that are included in n?1 error correction code frames of a first size, respectively, in the nonvolatile memory, the controller generates a second error correction code that constitutes an error correction code frame of a second size together with the n?1 data portions of the first unit and a second data portion to be written into the nonvolatile memory by encoding the n?1 data portions of the first unit and the second data portion, and writes the second data portion and the second error correction code into the nonvolatile memory.

Abstract: A memory system includes a memory device having a memory cell array, and a controller. The memory cell array includes a plurality of first units and at least one second unit. The second unit includes the plurality of first units. The controller counts a first number of times of read operation for each of the plurality of first units, and, in response to the first number of times for one first unit among the plurality of first units reaching a first value, updates a second number of times for the second unit that includes the one first unit. In response to the second number of times reaching a second value, the controller determines whether to rewrite data stored in at least one of the first units included in the second unit.

Abstract: According to one embodiment, a storage device comprises a nonvolatile memory, and a controller configured to perform a first data write operation in a first mode, and to perform a second data write operation in a second mode. Data of a first number of bits is written per memory cell in the first mode. Data of a second number of bits is written per memory cell in the second mode. The second number is larger than the first number. The controller reserves one or more free blocks as write destination block candidates of the first data write operation, perform the first data write operation for one of the write destination block candidates, and perform a garbage collection.

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.