Memory device including main memory storage and distinct key storage accessed using only a row address

摘要

A data memory unit including a main memory data storage portion that is accessed by a row address and a column address representing all of the bits of a given address and a main memory key data storage portion that is accessed by just the row address which is fewer that all of the bits of the given address are integrated into a single semiconductor chip. A data storage apparatus is composed of a plurality of such data memory units. The main memory key data storage portion can be increased at the same time as when the capacity of the main memory is increased, thereby simplifying the process of increasing main memory size.