说明：  文介绍一种用单片机普通I/O 口实现串行通信的方法，可在单片机的最小应用系统中实现与两个以上串行接口设备的多机通信。附有电路图和源代码。
(text introduces a microcontroller I/O port serial communications, in the smallest single-chip microcomputer application system to achieve more with two serial interfaces of multi-machine communication. With circuit and the source code.)