串行通信MCS-51单片机内部有一个全双工的串行通信口，即串行接收和发送缓冲器（SBUF），这两个在物理上独立的接收发送器，既可以接收数据也可以发送数据。但接收缓冲器只能读出不能写入，而发送缓冲器则只能写入不能读出，它们的地址为99H。这个通信口既可以用于网络通信，亦可实现串行异步通信，还可以构成同步移位寄存器使用。-MCS-51 microcontroller serial communication within the a full-duplex serial communication port, that is, the serial receive and send buffer (SBUF), these two physically separate receiver transmitter, both can receive data can be sent data. Only read by the receiving buffer can not write, but can only write to send the buffer is not allowed to deliver, their address is 99H. The communication port can be used for both network communications, can also achieve the serial asynchronous communication, but also constitute a synchronous shift register to use.