Why cellular automata are better than LFSRs as built-in self-test generators for sequential-type faults

Abstract

This paper presents a combinatorial method of evaluating the effectiveness of linear hybrid cellular automata (LHCA) and linear feedback shift registers (LFSR) as generators for stimulating faults requiring a pair of vectors. We provide a theoretical analysis and empirical comparisons to see why the LHCAs are better than the LFSRs as generators for sequential-type faults in a built-in self-test (BIST) environment. Based on the concept of a partner set, the method derives the number of distinct k-cell substate vectors which have 2/sup 2k/, 1/spl les/k/spl les/[n/2], transition capability for an n-cell LFSR and an n-cell LFSR with maximum length cycles. Simulation studies of the ISCAS85 benchmark circuits provide evidence of the effectiveness of the theoretical metric. >