PURPOSE: To prevent wasteful power consumption without energizing a memory in which nothing is stored by permitting a selection means to select a memory element corresponding to a signal for selectively designating plural memory elements if the selection means receives the signal and at least allowing feeding to the selected memory element.

CONSTITUTION: A memory controller 12 is connected with an address controller 10 through signal lines 20 and it has a function selecting the memory chips 14 by the selection signal of the address controller 10. The address controller 10 is connected with a terminal 28 through a signal line 26 and a receives having encoded chip select data for selecting the memory chips 14 from the terminal 28 at the time of writing/reading data. With chip select data, the selection signals of the memory chips 14 are transmitted to the memory controller 12. Since feeding is controlled at every memory chip 14, and feeding is not executed to the memory chips which are not energized in chip select outputs 24, wasteful power is not consumed.