Algorithms for the compilation of regular expressions into PLAs

The language of regular expressions is a useful one for specifying certain sequential processes at a very high level. They allow easy modification of designs for circuits, like controllers, that are described by patterns of events they must recognize and the responses they must make to those patterns. This paper discusses the compilation of such expressions into specifications for programmable logic arrays (PLAs) that will implement the required function. A regular expression is converted into a nondeterministic finite automaton, and then the automaton states are encoded as values on wires that are inputs and outputs of a PLA. The translation of regular expressions into nondeterministic automata by two different methods is discussed, along with the advantages of each method. A major part of the compilation problem is selection of good state codes for the nondeterministic automata; one successful strategy and its application to microcode compaction is explained in the paper.