Efficient self-timed interfaces for crossing clock domains

With increasing integration densities, large chip designs are commonly partitioned into multiple clock domains. While the computation within each individual domain may be synchronous, the interfaces between these domains often use asynchronous methods. One such approach is the STARI technique where a self-timed FIFO compensates for clock-skew between the sender and receiver. We present implementations of STARI where the FIFO consists of a single, handshaking stage. We start with the simplest case where the sender and receiver operate at exactly the same frequency with an unknown skew. We then generalize this design for links with clocks whose frequencies are rational multiples of each other, clocks whose frequencies are closely matched, and arbitrary clocks. We show that in each of these cases, the STARI interface can exploit the stability of typical clocks to achieve low latencies and negligible probabilities of synchronization failure using very simple hardware.