/*在p1.0上產(chǎn)生一個(gè)占空比變化的脈沖信號(hào)，它產(chǎn)生的脈寬調(diào)制信號(hào)用于電機(jī)的變速控制*/   
#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中斷服務(wù)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  /*外中斷1服務(wù)程序*/   
{union{uint word;   
   
       struct {uchar hi;   
               uchar lo;}byte;   
   
       }newcount;   
newcount.byte.hi=TH1;   
newcount.byte.lo=TL1;   
period=newcount.word-oldcount;   /*測得周期*/   
oldcount=newcount.word;   
one_round=1;                    /*每轉(zhuǎn)一圈，引起中斷，設(shè)置標(biāo)志*/   
}   
   
   
void main(void)   
{   
  IP=0x04;           /*設(shè)置INT1為高位優(yōu)先級(jí)*/   
  TMOD=0x11;         /*T0 T1  16位方式*/   
  TCON=0x54;            //T0 T1 運(yùn)行，IT1邊沿觸發(fā)/    
  TH1=0;TL1=0;   
  IE=0x86;         //允許中斷EX1,ET0/    
  for( ; ; )   
  {if(one_round)   
     {if(period<TARGET) if(percent else *占空比減* ++percent;} *占空比增* {if(percent<100)>0)--percent;   
   one_round=0;}   
   }   
}