SEMICONDUCTOR MEMORY DEVICE AND ITS DRIVING METHOD

PROBLEM TO BE SOLVED: To provide a semiconductor memory device capable of preventing an false operation caused by an illegal code when a MRS command is applied, and its driving method. SOLUTION: The semiconductor memory device is provided with a first latch that latches a MRS code of multiple bits in response to a MRS (Mode Register Set) command pulse, a code controller that generates a control signal in response to a code value of preset bits out of an output signal from the first latch, a second latch that selectively latches the output signal from the first latch, and a mode decoder that decodes an output signal from the second latch to output an operation mode signal. When a MRS code corresponding to a specific operation mode constituted of a combination of addresses of multiple bits is applied as an illegal code, the false operation is prevented by enabling all the MRS codes including own to maintain previous states. COPYRIGHT: (C)2009,JPO&INPIT