Formal Verification of an Arbiter

We present the circuit-level verification of a common arbiter circuit. To perform this verification, we address three issues. First, we present a specification for the arbiter and show how this specification amounts to a set of topological constraints on trajectories of the continuous model. Second, we show that computing bounding sets for these trajectories is complicated by stiffness of the differential equation model and present novel techniques for handling stiff equations in a formal verification context. Finally, we note that while no arbiter can be guaranteed to always grant a pending request, we can show liveness in the presence of concurrent requests in an “almost surely” sense.