00.c

在p1.0上产生一个占空比变化的脉冲信号

/*在p1.0上产生一个占空比变化的脉冲信号，它产生的脉宽调制信号用于电机的变速控制*/
#include <reg51.h>
#define uchar unsigned char
#define uint unsigned int

uchar time,status,percent,period;
bit one_round;
uint oldcount,target=500;

void pulse(void) interrupt 1 using 1 /*T/C中断服务程序  1ms--10MHz*/
{TH0=-833/256;
 TL0=-83%256;
  ET0=1;
   if(++time==percent)P1=0;
   else if(time==100)
     {time=0;
      P1=1;}
}

void tachmeter(void) interrupt 2 using 2  /*外中断1服务程序*/
{union{uint word;

       struct {uchar hi;
               uchar lo;}byte;

       }newcount;
newcount.byte.hi=TH1;
newcount.byte.lo=TL1;
period=newcount.word-oldcount;   /*测得周期*/
oldcount=newcount.word;
one_round=1;                    /*每转一圈，引起中断，设置标志*/
}


void main(void)
{
  IP=0x04;           /*设置INT1为高位优先级*/
  TMOD=0x11;         /*T0 T1  16位方式*/
  TCON=0x54;        	//T0 T1 运行，IT1边沿触发/
  TH1=0;TL1=0;
  IE=0x86;         //允许中断EX1,ET0/
  for( ; ; )
  {if(one_round)
     {if(period<target)
       {if(percent<100)  /*占空比增*/
          ++percent;}    /*占空比减*/
      else if(percent>0)--percent;
   one_round=0;}
   }
}