说明：  下面我们根据8251A芯片的使用体会对其在串行同步方式下的通信原理及应用进行着重介绍。在开始发送或接收之前，8251A必须装入一组由CPU 产生的控制字。
(below 8251A chip based on the use of its experience in serial synchronous mode of communication theory and application highlights. At the beginning of sent or received before the 8251A must be loaded by a group of CPU controlled characters.)