Formal hardware verification systems can be split into two categories: theorem proving systems and automatic finite state machine based systems. Each approach has its own complementary advantages and disadvantages. In this paper, we consider the combination of two such systems: HOL (a theorem proving system) and MDG (an automatic system). As HOL hardware verification proofs are based on the hierarchical structure of the design, submodules can be verified using other systems such as MDG. However, the results of MDG are not in the appropriate form for this. We have proved a set of theorems that express how results proved using MDG can be converted into the form used in traditional HOL hardware verification.

Abstract. In this report, we investigate the impact of design changes on formal verification using MDG (Multiway Decision Graphs) tools. In particular, we would like to determine whether the design changes that make verification by interactive theorem proving simpler, also make verification by automated decision diagram approach simpler as well. The design we consider is the Fairisle 4 by 4 switch fabric which is in use for real applications in the Cambridge ATM Fairisle network. A major consideration during the design change decisions should not compromise other design goals such as performance and functionality. The specification and verification obtained in MDG demonstrated the expected positive impact of these design changes. 1.

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