The OKI MSM534022E is a high-speed CMOS Mask ROM that can electrically switch between 262,144-word x 16-bit and 524,288-word x -bit configurations. The MSM534022E operates on a single 5.0V power supply and is TTL compatible. The chip's asynchronous I/O requires no external clock assuring easy operation. A power-down mode provides low power dissipation when the chip is not selected. The CE and OE pins are provided as control signals that permit three-stated output allowing easy memory expansion on a system bus. The MSM534022E is suited for use as large capacity fixed memory for microcomputers and data terminals.