直流电机调速，通过PWM控制直流电机的转速-DC motor speed DC motor speed by PWM control

本程序是直流电机控制实验，程序采用定时中断产生PWM方波，100次中断为一个周期。-This procedure is a DC motor control experiment, procedures used interrupted from time to time have a PWM square wave, 100 times a cycle of disruption.