In this SBIR effort, Arkansas Power Electronics International, Inc. (APEI, Inc.) and the University of Arkansas are partnering to develop a versatile, radiation-hardened, low-power, asynchronous 8051-based microcontroller capable of functioning in a very wide temperature range (-230 o
C to +150 o
C). To make the asynchronous microcontroller as seamless as possible with existing technology, the proposed asynchronous 8051 microcontroller will be developed to be pin-to-pin compatible with the commercial 8051, as well as compatible with the existing commercial software suites. The 8051 is considered the world's most popular microcontroller core, therefore demonstration of the design methodology on this platform allows for quick adoption -- extensive software libraries, advanced compilers, and well-trained software developers are readily available to support integration.