学习单片机按键中断功能切换看了一段代码有地方无法理解

ID:960619 · 发表于 2021-8-19 18:08

请教下，这单片机代码中的P0起到什么作用？

#include<reg52.h>//#include "stc8.h"//

sbit beep=P1^5;
sbit k1=P3^1;
sbit k3=P3^2;//外部中断0 p32
sbit led=P2^0;
#define N P2

unsigned char num;
unsigned char aa;

void delay(unsigned int i)
{
      while(i--);
}
void fmq()//蜂鸣器
{
      beep=~beep;
      delay(100);
}
void led0()//流水灯
{
      N=0xff;
      N=0xfe;
      fmq();
      delay(50000);
      if(num!=0){return;}
      P0=0xfe;

      N=0xfd;
      fmq();
      delay(50000);
      if(num!=0){return;}
      P0=0xfe;

      N=0xfb;
      fmq();
      delay(50000);
      if(num!=0){return;}
      P0=0xfe;

      N=0xf7;
      fmq();
      delay(50000);
      if(num!=0){return;}
      P0=0xfe;

      N=0xef;
      fmq();
      delay(50000);
      if(num!=0){return;}
      P0=0xfe;

      N=0xdf;
      fmq();
      delay(50000);
      if(num!=0){return;}
      P0=0xfe;

      N=0xbf;
      fmq();
      delay(50000);
      if(num!=0){return;}
      P0=0xfe;

      N=0x7f;
      fmq();
      delay(50000);


  if(num!=0){return;}
      P0=0xfe;
}

void led1()//led对称亮
{
      while(1)
      {
            N=0x7e;
            fmq();
            delay(35000);
            //delay(35000);
            if(num!=1){break;}
            P0=0xfc;

            N=0xbd;
            fmq();
            delay(35000);
            //delay(35000);
            if(num!=1){break;}
            P0=0xfc;

            N=0xdb;
            fmq();
            delay(35000);
            //delay(35000);
            if(num!=1){break;}
            P0=0xfc;

            N=0xe7;
            fmq();
            delay(35000);
            //delay(35000);
            if(num!=1){break;}
            P0=0xfc;

            N=0xe7;
            fmq();
            delay(35000);
            //delay(35000);
            if(num!=1){break;}
            P0=0xfc;

            N=0xdb;
            fmq();
            delay(35000);
            //delay(35000);
            if(num!=1){break;}
            P0=0xfc;

            N=0xbd;
            fmq();
            delay(35000);
            //delay(35000);
            if(num!=1){break;}
            P0=0xfc;

            N=0x7e;
            fmq();
            delay(35000);
            //delay(35000);

            if(num!=1){break;}
            P0=0xfc;
  }
}
void led2()//led分别单双数亮
{
      while(1)
      {
            N=0xaa;
            fmq();
            delay(50000);
            delay(50000);
            if(num!=2){break;}
            P0=0xf8;

            N=0x55;
            fmq();
            delay(50000);
            delay(50000);
            P0=0xf8;
            if(num!=2){break;}
            P0=0xf8;
}

}
void led3()//通过按键k1使led一个一个亮
{
      unsigned int i;
      N=0xfe;
      while(1)
      {
            if(k1==0)
            {
               switch(i)
                     {
                     case(0):N=0xfd;fmq();i++;break;
                     case(1):N=0xfb;fmq();i++;break;
                     case(2):N=0xf7;fmq();i++;break;
                     case(3):N=0xef;fmq();i++;break;
                     case(4):N=0xdf;fmq();i++;break;
                     case(5):N=0xbf;fmq();i++;break;
                     case(6):N=0x7f;fmq();i++;break;
                     case(7):N=0xff;fmq();i++;break;
                     }
               while(!k1);

            }

            if(i>=8){i=0;break;}
            P0=0xf0;
            if(num!=3){break;}
      }
}

void init()//中断初始化
{
      IT0=1;//外部中断0 跳变触发
      EX0=1;//外部中断0 p32
      EA=1;
}
void main()
{

      init();

      while(1)
      {

                     switch(num)
                     {
                     case(0):led0();
                                    P0=0xfe;
                                    break;
                     case(1):led1();
            P0=0xfc;
                                    break;
                     case(2):led2();
                                    P0=0xf8;
                                    break;//num++;
                     case(3):led3();
                                    P0=0xf0;
                                    break;

                     }

      }

}

void init0() interrupt 0//中断程序 k3
{
      //EX0=0;

      if(num==0){P0=0xfe;}
      num=num+1;

      if(num==1){P0=0xfc;}
      if(num==2){P0=0xf8;}
      if(num==3){P0=0xf0;}

  if(num>3){num=0;}

      //EX0=1;
}