51单片机产生频率、占空比可调的方波即PWM波

#include
#define uint unsigned int
#define uchar unsigned char
#define HIGH 10 //HIGH与ALL的比值为占空比
#define ALL 20 //ALL为周期时间，即20ms，改变数值即可改变周期
sbit out=P1^0;
uint tt;
void main()
{
TMOD=0x01; //设置定时器0为工作方式1
TH0=(65536-1000)/256; //设置初值
TL0=(65536-1000)%256;
EA=1; //开总中断
ET0=1; //开定时器0中断
TR0=1; //启动定时器0
out=1;
while(1);
}

void timer0() interrupt 1
{
TH0=(65536-1000)/256; //重装初值
TL0=(65536-1000)%256;
tt++;
if(tt==HIGH)
out=0;
if(tt==ALL)
{
out=1;
tt=0;
}
}

/* THAT IS ALL. THANK YOU. */