说明：  在单片机通过软件建立定时器，原则上可以建立无数个，在硬件定时器不够用时，可以考虑使用，或是当作练习使用，对于熟悉单片机的编程很有好处
(in SCM software through the establishment timer can, in principle, the establishment of numerous, the hardware timer is not enough, may consider the use, or use as a practice, for those familiar with microcontroller programming very good)