In this paper, we present methods for synthesizing multilevel asynchronous circuits to be both hazard free and completely testable. Making an asynchronous two-level circuit hazard free usually requires the introduction of either redundant or nonprime cubes or both. This adversely affects the circuit's testability. However, using extra inputs, which is seldom necessary, and a synthesis-for-testability method, we convert the two-level circuit into a multilevel circuit that is completely testable. To avoid the addition of extra inputs as much as possible, we introduce new exact minimization algorithms for hazard-free two-level logic where we first minimize the number of redundant cubes and then minimize the number of nonprime cubes. We target both the stuck-at and robust path delay fault models using similar methods. However, the area overhead for the latter may be slightly higher than for the former.
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