The UT28F256 amorphous silicon anti-fuse PROM is a high performance, asynchronous, radiation-hardened, 32K x 8 programmable memory device. The UT28F256 PROM features fully asychronous operation requiring no external clocks or timing strobes. An advanced radiation-hardened twin-well CMOS process technology is used to implement the UT28F256. The combination of radiation-hardness, fast access time, and low power consumption make the UT28F256 ideal for high speed systems designed for operation in radiation environments.