说明：  1)了解8251的内部结构、工作原理及与8086的接口逻辑。 2)掌握对8251的初始化编程方法，学会使用8251实现设备之间的串行通信。 3)设计8251的硬件连接及编写程序，实现自发自收。
(1) to understand the 8251' s internal structure, working principle and with the 8086 interface logic. 2) to master the 8251 initialization programming method, learn to use 8251 serial communication between devices. 3) design of the 8251 hardware connections and programming, spontaneous collected.)