///////////////////////////////////////////////////////////////////
// 8位累加器測速程序(PACN3累加器),PT3口輸入脈沖
//每次記錄脈沖時間可修改宏:TIME_INTER
//說明此程序用于總線時鐘在32M情況下,若總線時鐘有變化,改分頻參數(shù)和模數(shù)常數(shù)以得到精確定時 (MCCTL和MCCNT)
////author:whut_wj

///////////////////////////////////////////////////////////////////
#include <hidef.h>      /* common defines and macros */
#include <mc9s12dg128.h>     /* derivative information */
#pragma LINK_INFO DERIVATIVE "mc9s12dg128b"

#define TIME_INTER 1000  //1000個ms=1s
byte Get_pulse;           //脈沖個數(shù)


void Start_PLL(void)   //busCLK=32M
{
  REFDV=0x01;          // PLLCLK =2*OSCCLK*(SYNR + 1)/(REFDV + 1)
  SYNR=0x03;	         //        =2*16M*3/2=64M
  asm{
    BRCLR CRGFLG,#$08,*
    BSET CLKSEL,#$80
    }													  
}


void PACN3Init()
{
  TCTL4=0X80;   
  ICPAR=0x08;
  PACN3=0X00;

}


void MDCInit(void)
{
  MCCTL = MCCTL&0Xfb; //模數(shù)計數(shù)器禁止運行
  MCCTL = 0Xe3;       //允許中斷，模數(shù)計數(shù)方式 
                      //返回時重新加載所用的常數(shù)，分頻常數(shù)為16 
  MCCTL = MCCTL|0X04; //模數(shù)計數(shù)器使能
  MCCNT = 2000;       //(1/32M)*16*2000= 1ms 
  MCCTL = MCCTL|0X08 ; //把模數(shù)常數(shù)寄存器的值加載到模數(shù)計數(shù)器FLMC;
}

 

void main(void) 
{
  DisableInterrupts;
  Start_PLL();
  PACN3Init();
  MDCInit();
  EnableInterrupts;
  DDRB=0xff;
  PORTB=0XAA; 
  for(;;)
   {

   } 
}


#pragma CODE_SEG __NEAR_SEG NON_BANKED
void interrupt 26 MDC_ISR(void) 
{ 
  static unsigned int number_count;
  MCFLG = 0x80; 
  number_count ++;

  if( number_count==TIME_INTER)        //1秒取一次
    {
    Get_pulse = PACN3; 
    PACN3 = 0X00;
    number_count=0;
    PORTB^=0Xff;
    }
}