*pwm 調(diào)制程序*/

/*說(shuō)明： key用來(lái)控制 脈寬的高電平時(shí)間，
可以在P2.0引腳 接一個(gè)led做測(cè)試*/ 
＃i nclude <reg51.h>

#define CIRCLE 10

void pwmkey(void);

unsigned char count=1,last;

sbit led=P2^0;
sbit key=P0^0;

void main(void)
{
 EA=1;
 ET0=1;
 TH0=(65536-1000)/256;
 TL0=(65536-1000)%256;
 TR0=1;
 count=1;
 last=1;
 
 while(1)
 {
  pwmkey();
 }
}

void pwmkey(void)
{
 char old=0 ,new=0;
 while(1)
 {
  new=key;
  if(new && !old)
   last++;
  if(last>CIRCLE)
   last=1;
  old=new;
 }
}

void into(void) interrupt 1
{
 count++;
 if(count>CIRCLE) 
 {
  count=1;
 } 
 if(count<=last)
  led=0;
 else  
   led=1;
 TH0=(65536-1000)/256;
 TL0=(65536-1000)%256;
}