51单片机实现PWM波占空比可调.docx

51单片机实现PWM波占空比可调平台：STC89C52名称：本程序为用单片机制作的占空比均匀间隔可调PWM发生器。占空比可调间隔为0.1。即可取得占空比为0%，10%，20%……90%到100%的PWM波。该波的频率固定为1KH（周期1000微秒）。SY-1学习板上的操作键：S2----占空比加S3----占空比减晶振:11.0592MHZ程序代码：#includereg52.h#define uint unsigned int uint pp;char num=2,dis;sbit pwm=P1^0;sbit s2=P3^4;sbit s3=P3^5;sbit dula=P2^6;sbit wela=P2^7;unsigned char code table[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71,0x00};void keyscan(){if(s2==0){while(!s2);num++;if(num==11)num=10;dis=num;}if(s3==0){while(!s3);num--;if(num==-1)num=0;dis=num;}}void display(a){ dula=0; P0=table[a]; dula=1; dula=0; wela=0; P0=0xfe; wela=1; wela=0; }void main(){TMOD=0x01; //模式设置可见采用的是定时器0，工作与模式1（M1=0，M0=1）。TR0=1; //打开定时器TH0=0Xff; //定时器设置，每隔100微秒发起一次中断。TL0=0Xa4;ET0=1; //开定时器0中断EA=1; //开总中断while(1){keyscan();if((num!=0)(num!=10))//对于占空比为0和100%这两种极端情况，最好分离出，单独考虑{if(pp=num)pwm=1;elsepwm=0;}else if(num==0)//当占空比为0pwm=0;elsepwm=1;if(pp==10)//当占空比为100%pp=0;display(num);//显示num当前值，占空比为num/10。}}void time0() interrupt 1{TH0=0Xff;TL0=0Xa4;pp++;}