A case study for the verification of complex timed circuits: IPCMOS

The verification of a n-stage pulse-driven IPCMOS pipeline, for any n>0, is presented. The complexity of the system is 32n transistors and delay information is provided at the level of transistor The correctness of the circuit highly depends on the timed behavior of its components and the environment. To verify the system, three techniques have been combined: (1) relative-timing-based verification from absolute timing information, (2) assume-guarantee reasoning to verify untimed abstractions of timed components and (3) mathematical induction to verify pipelines of any length. Even though the circuit can interact with pulse-driven environments, the internal behavior between stages commits a handshake protocol that enables the use of untimed abstractions. The verification not only reports a positive answer about the correctness of the system, but also gives a set of sufficient relative-timing constraints that determine delay slacks under which correctness can be maintained.