PhD Thesis

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« Reflections on the methodology for verifying multi-clock design : qualitative analysis and automation ».

Author: M. Kebaili
Advisor: K. Morin-Allory
Co-advisor: J.C. Brignone
President of jury: B. Rouzeyre
thesis reviewer(s): E. Encrenaz-Tiphene, S. Pillement,
thesis examinator(s): R. Leveugle,
These de Doctorat Université Grenoble Alpes
Speciality: Microélectronique
Defense: October 25 2017
ISBN: 978-2-11-129230-7


For several years now, the digital IC market has been requiring both more complex systems and reduced production times. In this context, the semiconductor chip maker companies call on external IP providers offering components working on dedicated clock signals. When these IPs communicate between them, the source and destination clocks are not the same, we talk about "Clock Domain Crossing" (CDC). CDC correspond to asynchronous communications and can cause critical failures. Furthermore, due to the complexity and the random nature of CDC issues, they can not be exhaustively checked with methods such as timing analysis or functional simulation. With the increase of CDC in the digital designs, EDA tools providers have developed software solutions dedicated to CDC static verification. Whereas, the designs are subject to continuous change, the verification tools are not able to be up to date. To resolve these practical issues, the CDC industrial verification is based on the specification of constraints and exclusions by the user. This manual flow, which replaces the tools, can mask bugs. Moreover, the human effort required by this approach is incompatible with the time allowed to industrial designs development. Our goal has been to automate the verification submitting solutions based on formal properties. The work consisted in the analysis of the different CDC design and verification approaches through the evaluation of main CDC checker tools. From the results obtained, we have formalized the practical problems and proposed models to obtain automatically exhaustive results. The tests have been performed on a processor-based subsystem (CPUSS) developed at STMicroelectronics. Adopting our models enables a complete checking of CPUSS in an automatic way, which is essential within a competitive industrial environment. Actually, the amount of information to be specified by the user has been reduced by half for each one of the evaluated tools. Otherwise, this work has shown that the development axis of the CDC tools despite the addition of functionalities such as hierarchical flows or fault injection, doesn’t improve the quality of results (QoR). Since a collaboration has been established with the main tool providers some solutions would probably be included into the tools over the coming years.

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