Metastability in Latches, Arbiters and Data-convertors

Real-time digital systems and asynchronous computer systems have an inherent risk of occasional failures due to metastability in various components used to control data-transfers. This possibility has been known for a long time, although it is sometimes forgotten or overlooked. There is renewed interest in asynchronous computer systems because of the prospects they offer for lower power operation and improved electromagnetic compatibility compared to conventional fully synchronous systems. As a result, design approaches to minimise metastability effects need to be adopted. Recent increased understanding of non-linear dynamics and the availability of software for the accurate simulation and visualisation of dynamic behaviour enables metastability to be investigated and demonstrated much more readily. This paper provides a mainly-tutorial review of how metastability arises in various commonly-used components, illustrated with the results of simulations.