用8251A实现串行口异步方式双机通信，波特率1200bps。采用查询方式发送、中断方式接收。双方平时处在查询键盘、等待中断接收状态，并显示相关提示。-Asynchronous serial interface with the 8251A to achieve two-way machine communication, baud rate 1200bps. Using query mode to send, receive interrupt. Look at the two sides usually the keyboard, waiting for interrupt reception state, and display relevant prompts.