An ATPG-based framework for verifying sequential equivalence

Abstract

In this paper, we address the problem of verifying the equivalence of two sequential circuits. State-of-the-art sequential optimization techniques such as retiming and sequential redundancy removal can handle designs with up to hundreds or even thousands of flip-flops. The BDDbased approaches for equivalence checking can easily run into memory explosion for such designs. With an attempt to handle larger circuits, we modify the test pattern generation techniques for verification. The suggested approach utilizes the efficient backward justification technique popularly used in most sequential ATPG programs. The method explores the structural similarity between circuits under verification, and performs the verification in stages to improve the efficiency. An effective algorithm to identify equivalent flip-flops is presented. This ATPGbased framework is suitable for verifying circuits with or without a reset state. Experimental results of verifying the correctness of circuits after sequential redundancy removal will be presented.