说明：  单片机并行I/O口数量总是有限的，有时并行口需作其他更重要的用途，一般也不会用数量众多的并行I/O口专门用来驱动显示电路，能否用80C51的串行通信口加上少量I/O及扩展芯片用于显示电路呢？答案是肯定的。 80C51的串行通信口是一个功能强大的通信口，而且是相当好用的通信口，用于显示驱动电路再合适不过了，下面我们就根据这种需要设计一个用两个串行通信口线加上两根普通I/O口，设计一个4位LED显示电路。当然只要再加上两根I/O口线即可轻易实现8位LED的显示电路。
(SCM parallel I/O I always limited quantity, and sometimes parallel port need for other more important uses, generally will not be used for a large number of parallel I/O I show devoted to the drive circuit 80 C51 able to use the serial communication port with a small amount of I/O and expansion of chips for the display circuit? The answer is yes. 80C51 Serial Communications mouth is a powerful communications mouth, but is very handy communications mouth, for the display driver circuit could not have been more appropriate, Now we need to design the basis of this one with two serial communication lines with two general I/O Hau, Design of a four LED display circuit. Of course if coupled with two I/O lines I could easily achieved eight LED display circuit.)