| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor memory device and a memory system which perform standing-by in low power consumption when there is no need for read/write access and perform access without a delay when read/write access is required, and to provide a refresh control method for a semiconductor memory device. SOLUTION: The a semiconductor memory device has an operation mode in which read/write operation is performed in response to a command supplied externally in synchronization with a clock, and a power-down mode in which no external read/write command is accepted, and the device performs refresh in response to an externally supplied signal during the power-down mode. Since refresh control can be performed from a memory controller also in the power-down mode, access is performed without a delay after release of power-down. COPYRIGHT: (C)2010,JPO&INPIT |
