On effectiveness of phase shifters for pseudo-random test pattern generators

This paper investigates the effectiveness of add-on phase shifters for tree-structured linear cellular automata (TLCA) and conducts comparative studies of commonly used pseudo-random test pattern generators (PRPGs) with phase shifters. The pseudo-randomness of TLCA patterns (with and without phase shifters) and phase shifters built on different types of PRPGs are studied by means of visual test, correlation test, equidistribution test and linear independence test (Mrugalski et al, Proc. VLSI Test Symp., pp. 377-386, 2000). Our study shows that (1) add-on phase shifters do improve the pseudo-randomness of TLCA patterns, (2) the pseudo-randomness of TLCA patterns with phase shifters is comparable to but does not outperform that of LFSRs and LHCA (linear hybrid cellular automata) with phase shifters, (3) it is easier to realize low cost TLCA phase shifters (with 2 XOR gates) than for LFSRs.