Identifying sequential redundancies without search

Previous solutions to the difficult problem of identifying sequential redundancy are either based on incorrect theoretical results, or rely an unrealistic simplifying assumptions, or are applicable only to small circuits. In this paper we show the limitations of the existing definitions of sequential redundancy and introduce a new concept of c-cycle redundancy as a generalization of the conventional notion of sequential redundancy. We present an efficient algorithm, FIRES, to identify c-cycle redundancies without search. FIRES does not assume the existence of a global reset nor does it require any state transition information. FIRES has provably polynomial-time complexity and is practical for large circuits. Experimental results on benchmark circuits indicate that FIRES identifies a large number of redundancies. We show that, in general, the redundant faults identified by FIRES are not easy targets for state-of-the-art sequential rest generators.