US Patent 10026491 Semiconductor memory device and memory system

A semiconductor memory device includes memory cells, a sense amplifier unit including a first latch circuit, and a control unit configured to execute read and write operations on the memory cells. The control unit, while executing the write operation on the memory cells, responsive to a write suspend command followed by a read command, performs a data saving operation, the read operation, and a data restoring operation prior to resuming the write operation. The data saving operation includes transferring first data stored in the first latch circuit to an external device, the first data including at least a result of verify operation performed on the memory cells. The data restoring operation includes transferring the first data to the first latch circuit.