用8251a实现串行口异步通信，自发自收，波特率1200bps，采用查询方式发送，中断方式接受。自收结果显示于屏幕。按esc返回dos -8251a Serial port with asynchronous communication, spontaneous self-income, the baud rate 1200bps, using queries sent, interrupt to receive treatment. Since the close results show