US Patent 7742350 Semiconductor device

A word line WLA of A port is activated based on a clock signal ACLK, and a word line WLB of B port is activated based on a port setting signal RDXA indicating that A port is a selected state. In addition thereto, a bit line of B port is precharged. A state in a simultaneous access operation is reproduced by activating the word line WLB during a time period of activating the word line WLA regardless of a delay difference of the clock signal and maintaining Vds of an access transistor of A port at a constant value.