Asynchronous Behavior Related Retiming in Gated-Clock GALS Systems

Although retiming is a well known method to optimize various characteristics of synchronous circuits, this method has rarely been applied to the synchronous blocks of a Globally Asynchronous Locally Synchronous (GALS) system. In this paper, communication protocols of gated-clock based wrappers have been analyzed for applying retiming algorithm to improve performance. Through the introduction of a new algorithm, it will be shown that a careful application of retiming concepts will not only prevent metastability problems between synchronous blocks of a GALS system, it can also reduce the communication gaps among those blocks whereby increasing their operating frequency. To demonstrate the effectiveness of the proposed algorithm, a 3-stage pipeline implementation of 16N digital filter is used as a locally synchronous block. Our experiments show a 23.2% increase in filter’s operating frequency compared to other optimized circuits using original retiming algorithm and common reliable metastability-free methods.