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標(biāo)題: 關(guān)于單片機(jī)延時(shí)程序的延時(shí)時(shí)間是怎么計(jì)算的？ [打印本頁(yè)]

作者: 子u 時(shí)間: 2018-12-28 16:35
標(biāo)題: 關(guān)于單片機(jī)延時(shí)程序的延時(shí)時(shí)間是怎么計(jì)算的？
………………………………
sbit key1=P3^2;          //布防
sbit key2=P3^3;          //撤防
sbit key3=P3^4;          //緊急報(bào)警
sbit BUZZ=P0^4;          //蜂鳴器
sbit rsd=P2^4;          //熱釋電輸入
sbit yanwu=P2^5;
sbit LED_B=P2^3; //布防指示燈
sbit LED_S=P2^0; //發(fā)送消息指示燈

uint TIME_50ms=0;          //計(jì)時(shí)的最小分辨率50ms
uint time_continue;
uchar TIME_ALAM=0;
bit flag=0,flag_BF=0;
bit flag_time_start=0;
bit again=0;
bit flag_alam;
bit SOS;
bit flag_continue;
bit into_BF=0;

void delay(uint z)//延時(shí)函數(shù)
{
      uint x,y;
      for(x=z;x>0;x--)
      for(y=110;y>0;y--);
}

………………………………………………………………以上省略了一些無關(guān)定義初始化。以下程序的如何計(jì)時(shí)，延時(shí)多少是我不明白的。
void TIME()
{
      if(flag==0)
      {
            delay(50);
            TIME_50ms++;
            if(TIME_50ms%10==0)
            LED_B=!LED_B;
            if(TIME_50ms>=400)
            {
                     TIME_50ms=0;
                     flag_BF=1;
                     LED_B=0;
                     flag_time_start=0;
                     again=1;
            }
      }
      else
      {
            delay(50);
            TIME_50ms++;
            if(TIME_50ms%10==0)
            {
                     LED_B=!LED_B;
                     if(flag_alam==1)
                     {
                              if(flag_continue==0)
                              {
                                    flag_continue=1;
                                    time_continue=TIME_50ms;
                              }
                              BUZZ=!BUZZ;
                              if(TIME_50ms>=time_continue+100)
                              {
                                    BUZZ=1;
                                    flag_continue=0;
                                    flag_alam=0;
                                    time_continue=0;
                              }
                     }
            }
            if(TIME_50ms>=1200)
            {
                     LED_B=0;
                     TIME_50ms=0;
                     flag_time_start=0;
                     again=1;
            }
      }
}

33333.png (41.52 KB, 下載次數(shù): 38)

原理圖

作者: bucker 時(shí)間: 2018-12-28 20:57
就是根據(jù)時(shí)鐘和單片機(jī)每條指令消耗的機(jī)器周期來計(jì)算，軟件延時(shí)只能是個(gè)大概的值，不會(huì)很精準(zhǔn)。想要精準(zhǔn)的延時(shí)值，必須用硬件定時(shí)器。

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