三星2410用看门狗实现的定时 1us为单位中文注释-原创喽

 

static int delayLoopCount = FCLK/10000/10;

void delay(int nTime)
{
    // time=0: adjust the Delay function by WatchDog timer.
    // time>0: the number of loop time
    // resolution of time is 100us.
    int i,adjust=0;
    if(nTime==0)
    {
        nTime   = 200;
        adjust = 1;
        delayLoopCount = 400;
  //PCLK/1M,Watch-dog disable,1/64,interrupt disable,reset disable
        WTCON = ((PCLK/1000000-1)<<8)|(2<<3); //看门狗定时器的预分频值设置为 PCLK/1000000 分频值 为64
        WTDAT = 0xffff;                              //for first update          
        WTCNT = 0xffff;                              //resolution=64us @any PCLK      所以一个周期的时间是     64/1000000  s    即为64us
  //肯能误解的是这里conut值是递减的但是减一次就是64us 即到0xfffe时候 所以dat来补充的时候过了  ffff×64us时间还是很长的
        WTCON = ((PCLK/1000000-1)<<8)|(2<<3)|(1<<5); //Watch-dog timer start           打开
    }
    for(;nTime>0;nTime--)
        for(i=0;i<delayLoopCount;i++);    //测量80000个时钟周期内有几个64us  ，但是貌似还是不是很精确，因为最后一个在64us中间的情况好像没有考虑
    if(adjust==1)
    {
        WTCON = ((PCLK/1000000-1)<<8)|(2<<3);   //Watch-dog timer stop
        i = 0xffff - WTCNT;                     //1count->64us, 200*400 cycle runtime = 64*i us  测试结果给i这里仅仅只是第一次的效果，以后不会再有了
        delayLoopCount = 8000000/(i*64);         //200*400:64*i=1*x:100 -> x=80000*100/(64*i)    同上
    }
 /*           

 

 

                                                                                                                   1
 最终以后调用 每次使用的只有    ntime × delayloopcount × ------------- 
                                                                                                                PCLK

 

 

                                                     1
 可以有等式        80000  × -----------  =   i × 64 us
                                                    pclk

 

 

 所以你想要的是 ntime = 1 的时候 下面式子相等

                                                            1
   ntime × delayloopcount × -------------   = 1us
                                                          PCLK

 

 

                                                            8000000
 现在就开始假设了 delayloopcount = ------------------
                                                                                     1
                                                        80000 ×---------
                                                                                  pclk

 

 

                                                                 8000000
  带入上面看你得到了什么    1× -------------------------- = 1
                                                                 8000000
 
 
  */
}