介绍了基于单片机用PWM实现直流电机调整的基本方法，直流电机调速的相关知识，及

PWM调整的基本原理和实现方法。重点介绍了基于MCS一51单片机的用软件产生PWM信号的途径，并

介绍了一种独特的通过采用计数法加软件延时法实现PWM信号占空比调节的方法。对于直流电机速度控

制系统的实现提供了一种有效的途径。-This paper introduces a kind of method of DC —motor speed modification based on PWM theory by

the SCM．Showing some relative knowledge upon the DC—motor timing，the basic theory and the way to implement．

And it emphasizes on the way for carrying out PW M signals based on MCS一5 1．This paper still provides a method

for modifying the speed of DC—motor by way of taking count of data and time delay by software．It offers a sort of

eficient method for the DC motor speed—controlling system．