用VHDL实现占空比任意可调的PWM产生器。（程序逐行注释），有仿真图。PWM,即Pulse-Width Modulation 脉宽调制，常用于电机的控制中。-Using VHDL adjustable duty cycle of PWM generator. (Progressive program notes), a simulation map. PWM, i.e. Pulse-Width Modulation PWM, used to control the motor.