本设计是以80c51为控制核心的计时器，利用单片机课程实验开发板的数码管模块进行显示。

本设计依照球赛换人的原则，能够完成对上场人员与下场人员号码的设置与循环显示以便通知全场。

适用于单片机初学者学习练手-The design is based on 80c51 timer to control the core, using SCM course experiment module development board digital display. The design in accordance with the principles of game substitutions, able to complete the setup of the playing staff and the fate of staff numbers and cycle in order to inform the audience. Suitable for beginners to learn microcontroller practiced hand