PHY verification - Still an open problem

PHYs are devices that combine digital and analog circuits to transmit data over a physical medium. To reach higher data rates, PHYs are employing increasingly complex digital control of a greater number of analog characteristics. In addition to interacting digital and analog, complexity in a PHY results from interactions between other domains that are not easily compartmentalized. The verification engineer must consider interactions between analog and digital, discrete and continuous, normal and test-mode, clocks and logic, and physical and logical. For this reason, verification is a difficult problem. In this paper, we share our experience in PHY verification by explaining a number of design patterns that introduce cross-domain complexity. For each pattern, we suggest some techniques that can help others avoid pitfalls. We show why we feel that good solutions do not exist and indicate directions that might lead to a more unified solution to the PHY verification problem.