这是利用定时器实现单片机输出PWM信号的，所谓PWM，是指周期可控，占空比可控的脉冲信号，这里利用定时器的定时功能，实现IO口输出电平的控制，从而实现PWM-This is using microcontroller timer achieve output PWM signal, the so-called PWM, it is to point to cycle control, and occupies emptiescompared controllable pulse signal, using the timer here time function, to realize the control of the output level of IO mouth, so as to realize the PWM