Low-Latency No-Handshake GALS Interfaces for Fast-Receiver Links

In this paper we introduce a novel interface for Globally-Asynchronous, Locally-Synchronous systems which does not use any form of handshake to cross the gap between the clock domains. In particular, links in which the Receiver runs faster than the Transmitter are targeted. The interface works by finding an approximate ratio between the clock frequencies. Then, ratiochronous synchronizers that can tolerate clock drifts are employed to transmit data from the Transmitter to the Receiver clock domain. Thanks to the periodic properties of rationally-related systems, no handshake is employed and the average latency of the interface is decreased 75 % compared to state-of-the-art GALS interfaces. Additionally, the interface uses only standard cells and, save for a delay line, can be designed at Register Transfer Level.