main.c

飞思卡尔HCS12里的定时和计时的方案,列出例子,以供参考.MDC,这个比较好用,精确,容易计算

///////////////////////////////////////////////////////////////////
//10ms
//author:whut_wj

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


void Start_PLL(void)   //busCLK=20M
{
  REFDV=0x03;          // PLLCLK =2*OSCCLK*(SYNR + 1)/(REFDV + 1)
  SYNR=0x04;	         //        =2*16M*3/2=40M
  asm{
    BRCLR CRGFLG,#$08,*
    BSET CLKSEL,#$80
    }													  
}


void MDCInit(void)
{
  MCCTL = MCCTL&0Xfb;//模数计数器禁止运行
  MCCTL = 0Xe3;       //允许中断，模数计数方式 
                      //返回时重新加载所用的常数，分频常数为16  
  MCCTL = MCCTL|0X04; //模数计数器使能
  MCCNT = 12500; //(1/20M)*16*12500= 10ms 
  MCCTL = MCCTL|0X08 ; //把模数常数寄存器的值加载到模数计数器FLMC;
}

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


#pragma CODE_SEG __NEAR_SEG NON_BANKED
void interrupt 26 MDC_ISR(void) 
{ 

  PORTB^=0Xff;
  MCFLG = 0x80;
}