Formal Modeling and Verification of PCHB Asynchronous Circuits

Precharge half buffer (PCHB) is one of the major quasi-delay insensitive (QDI) asynchronous design paradigms, which has been utilized in several commercial applications due to its low power and inherent robustness. In industry, QDI circuits are often synthesized from a synchronous specification using custom synthesis tools. Design validation of the implemented QDI circuits mostly relies on extensive simulation, which may fail to detect corner-case bugs, especially in complex designs. Hence, a formal verification scheme for PCHB circuits is much needed. In this article, we present a formal verification methodology for PCHB circuits synthesized from a Boolean/synchronous specification, which is based on equivalence checking and can guarantee both safety (full functional correctness) and liveness (absence of deadlock). The approach is fast, scalable, and applicable to combinational as well as sequential PCHB circuits. We demonstrate the method using several multipliers, multiply and accumulate circuits (MACs), and IEEE International Symposium on Circuits and Systems (ISCAS) benchmarks.