LFSR seed computation and reduction using SMT-based fault-chaining

Abstract

We propose a new method to derive a small number of LFSR seeds for Logic BIST to cover all detectable faults as a first-order satisfiability problem involving extended theories. We use an SMT (Satisfiability Modulo Theories) formulation to efficiently combine the tasks of test-generation and seed-computation. We make use of this formulation in an iterative seed-reduction flow which enables the “chaining” of hard-to-test faults using very few seeds. Experimental results demonstrate that up to 79% reduction in the number of seeds can be achieved.