A Pausible Bisynchronous FIFO for GALS Systems

Many of the challenges of modern SoC design can be mitigated or eliminated with globally asynchronous, locally synchronous (GALS) design techniques. Partitioning a design into many synchronous islands introduces myriad asynchronous boundary crossings which typically incur high latency. We have designed a pausible bisynchronous FIFO that achieves low interface latency with a pausible clocking scheme. While traditional synchronizers have a non-zero probability of metastability and error, pausible clocking enables error-free operation by permitting infrequent slowdowns in the clock rate. Unlike prior pausible synchronizers, our circuit employs standard two-ported synchronous FIFOs, common circuit elements that integrate well with standard tool flows. The pausible bisynchronous FIFO achieves an average latency of 1.34 cycles across an asynchronous interface while using less energy and area than traditional synchronizers.