说明：  只有最初级的逻辑电路才使用单一的时钟。大多数与数据传输相关的应用都有与生俱来的挑战，即跨越多个时钟域的数据移动，本文将介绍怎样在同步设计中处理异步信号
(Only the most elementary logic circuits use a single clock. Most of data transmission and related applications have inherent challenges, that is, across multiple clock domain data movement, this article will introduce how to deal with the design of asynchronous synchronization signal)