An enhanced tree-structured scan chain for pseudo-exhaustive testing of VLSI circuits

As the test pattern requirement of a pseudo-exhaustive testing is fewer than the traditional exhaustive testing, many approaches and architectures are proposed to implement the pseudo-exhaustive testing. Although these methods and architectures employ LFSR to generate the exhaustive random test patterns could successfully cut down the test time, the same problem "invalid test patterns" should still be considered. To avoid the "invalid test patterns", it requires new strategy to solve this problem. Since different seeds dominate different simulation results, seed selection is not arbitrary any more. This paper illustrates the importance of the seed selection, and shows the influence causing by employing various seeds. A suggestive threshold stop point for new strategy, which tries to solve "invalid test patterns" problem, is also defined.