Abstract: A memory device is arranged in such a manner that an access-target memory cell is selected from a plurality of memory cells in accordance with the level of the byte-enable signal at the timing when the level of the corresponding row address strobe signal (/RAS signal) changes, and by this arrangement, the problem resided in the conventional memory device that it could not be decided as to whether a memory block in the DRAM core was to be a selected or non-selected byte until the fall of the corresponding column address strobe signal (/CAS signal), and thus the column decoder and the preamplifier that start operating at the fall of the /RAS signal could not be efficiently controlled is solved, and due to this, electric power that might otherwise be consumed at the time of executing a byte-unit access to the wide-bus DRAM can be reduced.