Our initial given a 50% duty cycle, the motor's rated speed of 360 r/min, and then press the key 1 is the forward simulation, through the simulation we find that the actual speed of the motor in about 130 / min, and the digital tube display is 125 r/min, this is because in the process of simulation is the presence of time delay and algorithm, resulting in certain error. At this time, the PWM waveform has oscilloscope can be seen to be 50% duty cycle.