dev-embedded Aaron Mavrinac mavrinac@gmail.com AS31 is a free 8051 assembler originally written by Ken Stauffer. Versions of AS31 found here include important bug fixes and added features, such as standard intel-hex output format for use with PAULMON2 and EPROM programmers. AS31 is a good tool for building small 8051-based projects that are written in 100% 8051 assembly language.