Pseudoexhaustive TPG with a provably low number of LFSR seeds

Linear Feedback Shift Registers (LFSRs) are the most efficient and popular pseudo-exhaustive test pattern generation (TPG) mechanism. The goal is to minimize the required test length with low hardware overhead while obtaining pseudo-exhaustive TPG. Primitive characteristic polynomials are widely used because they require only one seed but the candidate polynomials are few and our experiments show that often the pseudoexhaustive test length is prohibitive. In this paper, we present a novel pseudoexhaustive approach with provably low number of seeds where the characteristic polynomial is the product of a primitive and an irreducible polynomial satisfying certain conditions. Our experimental results on the ISCAS'85 benchmarks show that using the proposed method requires very low hardware overhead. The list of characteristic polynomials for pseudoexhaustive TPG is greatly enhanced and our experiments show that pseudoexhaustive TPG is more feasible.