A Low-latency GALS Interface Implementation

Abstract

With the VLSI technology improving rapidly, SoC has been becoming the most important VLSI application. However, clock distribution and low power have already become the two most important issues in SoC design. In addition, it's also a very important issue to integrate IPs that can perform operations correctly with different clocks. Asynchronous circuits may resolve these problems by removing the "clock" signal. But it's too hard to implement the whole circuits with asynchronous circuit. The GALS (Globally-Asynchronous Locally-Synchronous) design methodology can balance this problem via separating each synchronous design with asynchronous interface. Thus, each part of the circuit can perform operations with its own clock. The communication between different parts of the circuit can be achieved via asynchronous channels. The GALS provides a reliable communication between different modules. However, the latency of GALS interface may cause performance degradation seriously. Thus how to reduce the latency of GALS interface is significant. In this paper, we implemented a small and simple stretchable-clock based GALS wrapper with low-latency in Verilog HDL and synthesized the design with TSMC 0.13 mu m cell library. We also showed that the wrapper can operate correctly with modules which operate with great different clock frequencies. In addition, we also recommend adding FIFO storage element on the transmission path.