Multiple clock domain synchronization in a QBF-based verification environment

Abstract

Modern designs are growing in size and complexity, becoming increasingly harder to verify. Today, they are architected to include multiple clock domains as a measure to reduce power consumption. Verifying them proves to be a computationally intensive and challenging task as it requires their clocks to be synchronized. To achieve synchronization, existing Boolean satisfiability-based methodologies add hardware to combine the clock domains before transforming them into their iterative logic array representation (ILA). As a consequence, this results in the addition of redundant time-frames adding overhead during verification. This paper introduces a novel framework to verify designs with multiple clocks using Quantified Boolean Formula satisfiability (QBF). We first present a formulation that models an ILA representation with symbolic universal quantification to achieve synchronization. This is later extended with the use of a clock divider to overcome inefficiencies. The net effect is the reduction in the number of redundant time-frames. Furthermore, the usage of QBF results in significant memory savings when compared to traditional methods. Experiments on bounded model checking demonstrate memory reductions of 76% on average with competitive run-time performance.