The Hitachi HN27C4000 is a 4-Mbit UV erasable and electrically programmable ROM that is organized either as 524288-word x 8 bit or as 262144-word x 16 bit, featuring extra-high speed burst mode that gives two times faster 4-word or 8byte serial access than normal. And also high speed and fast programming are served as well as the existing Hitachi 4M device HN27C4096 and HN27C4001. Fabricated on advanced fine process and high speed circuitry technique, HN27C4000 makes high speed access time and low power dissipation in either active or stand-by mode. Therefore, it is suitable for all systems featuring high speed microprocessor such as the 80386, 80486, 68030, 68040 and so on.