//试验AT24C02EEPROM芯片程序
#include<reg51.h>
#include <intrins.h>
#define uint unsigned int
#define uchar unsigned char
unsigned char sec;        //定义计数值，每过1秒，sec加1
unsigned int tcnt;        //定时中断次数
bit  write=0;             //写24C08的标志；
sbit sda=P2^0;                          //IO口定义
sbit scl=P2^1;
sbit dula=P2^6;
sbit wela=P2^7;
unsigned char j,k;
void delay(unsigned char i)		//延时程序
{
  for(j=i;j>0;j--)
    for(k=125;k>0;k--);
}
uchar code table[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,				//数码管编码
                        0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};
void display(uchar bai_c,uchar sh_c)			//显示程序
{
   dula=0;
   P0=table[bai_c];		//显示百位
   dula=1;
   dula=0;

   wela=0;
   P0=0x7e;
   wela=1;
   wela=0;
   delay(5);

   dula=0;
   P0=table[sh_c];		//显示十位
   dula=1;
   dula=0;

   wela=0;
   P0=0x7d;
   wela=1;
   wela=0;
   delay(5);

}

/////////24C08读写驱动程序////////////////////
void delay1(unsigned char x)
{  unsigned int i;
  for(i=0;i<x;i++);
  ;}
void flash()
{  ;  ; }
void x24c08_init()  //24c08初始化子程序
 {scl=1; flash(); sda=1; flash();}
void start()        //启动I2C总线
{sda=1; flash(); scl=1; flash(); sda=0; flash(); scl=0; flash();}
void stop()         //停止I2C总线
{sda=0; flash(); scl=1; flash(); sda=1; flash();}
void writex(unsigned char j)  //写一个字节
{  unsigned char i,temp;
   temp=j;
   for (i=0;i<8;i++)
   {temp=temp<<1; scl=0; flash(); sda=CY; flash(); scl=1; flash();}
   scl=0; flash(); sda=1; flash();
}
unsigned char readx()   //读一个字节
{
   unsigned char i,j,k=0;
   scl=0; flash(); sda=1;
   for (i=0;i<8;i++)
   {  flash(); scl=1; flash();
      if (sda==1) j=1;
      else j=0;
      k=(k<<1)|j;
	  scl=0;}
   flash(); return(k);
}
void clock()         //I2C总线时钟
{
   unsigned char i=0;
   scl=1; flash();
   while ((sda==1)&&(i<255))i++;
   scl=0; flash();
}
////////从24c02的地址address中读取一个字节数据/////
unsigned char x24c08_read(unsigned char address)
{
   unsigned char i;
   start(); writex(0xa0);
   clock(); writex(address);
   clock(); start();
   writex(0xa1); clock();
   i=readx(); stop();
   delay1(10);
   return(i);
}
//////向24c02的address地址中写入一字节数据info/////
void x24c08_write(unsigned char address,unsigned char info)
{
   EA=0;
   start(); writex(0xa0);
   clock(); writex(address);
   clock(); writex(info);
   clock(); stop();
   EA=1;
   delay1(50);
}

void t0(void) interrupt 1 using 0  //定时中断服务函数
{
TH0=(65536-50000)/256; //对TH0 TL0赋值
TL0=(65536-50000)%256; //重装计数初值
tcnt++;        //每过250ust tcnt加一
if(tcnt==20)  //计满20次（1秒）时
  {
    tcnt=0;   //重新再计
    sec++;
    write=1;  //1秒写一次24C08
    if(sec==100) //定时100秒，在从零开始计时
      {sec=0;}
  }
}

void main()
{
unsigned char i;
TMOD=0x01;  //定时器工作在方式1
ET0=1;  EA=1;
x24c08_init();        //初始化24C08
sec=x24c08_read(2);//读出保存的数据赋于sec
TH0=(65536-50000)/256; //对TH0 TL0赋值
TL0=(65536-50000)%256; //使定时器0.05秒中断一次
TR0=1;           //开始计时
 while(1)
  {
      i=10;
      while(i--)
      {
 	display(sec/10,sec%10);
      }
	if(write==1) //判断计时器是否计时一秒
       {
	 write=0;              //清零
          x24c08_write(2,sec);  //在24c08的地址2中写入数据sec
       }
   } 
}