Unbounded Protocol Compliance Verification Using Interval Property Checking With Invariants

We propose a methodology to formally prove protocol compliance for communication blocks in System-on-Chip (SoC) designs. In this methodology, a set of operational properties is specified with respect to the states of a central finite state machine (FSM). This central FSM is called main FSM and controls the overall behavior of the design. In order to prove a set of compliance properties, we developed an approach that combines property checking on a bounded circuit model with an approximate reachability analysis. The property checker determines whether a property is valid for an arbitrary state of the design regardless of its reachability. In order to avoid false negatives, reachability constraints are added to the property, which are generated by an approximate FSM traversal algorithm. We show how the existence of a main FSM can be exploited systematically in the reachability analysis and how to partition both the transition relation and the state space such that the computational complexity is reduced drastically. This makes formal verification of protocol compliance tractable even for large designs with several thousand state variables. Our approach has been applied successfully to verify several industrial designs.