A high performance 256K (512K) static ROM

A 256K ROM, fully expandable to 512K, has been fabricated. The ROM utilizes 2.5-/spl mu/m NMOS multiple threshold technology. It has a typical access time of 120 ns and uses push-pull circuitry to achieve an active current of 60 mA and a standby current of 1.9 mA. Total chip size is 39K mil/SUP 2/ for the 256K version. A modified X-cell has been chosen which requires 7.5 /spl mu/m. Current sensing was chosen to optimize access time.