这里使用AT89S51做实验,因无内建PWM功能(W78E65有),所以使用计时器来产生PWM波,改变流过LED的电压来产生灯明暗变化。-As used herein, AT89S51 do experiments, because there is no built-in PWM function (W78E65 there), so use a timer to generate PWM wave, changing the voltage flowing through the LED to produce light shading.