void send_ack(u8 ack)

{

      if(ack==1)

      {

            SDA_HIGHT;

      }

      else

      {

            SDA_LOW;

      }

      SCL_HIGHT;

      SCL_LOW;    

}   

u8 read(void)

{

      u8 r_data=0,i;

      SDA_HIGHT;

      for(i=0;i<=7;i++)

      {

            SCL_HIGHT;

            if(SDA_INPUT==1)

            {

                 r_data++; 

            }

            else

            {

                  ;

            }

             if(i!=7)          //***********注意************

             {

                  r_data<<=1;      

             }    

             SCL_LOW;

      }

      send_ack(0);

      return r_data;

}

void main(void)

{

      init();

      start();

      write(0xa0);

      write(0x20);

      write(0x55);

      stop();

      delay_ms(15);                                        

      start();

      write(0xa0);

      write(0x20);

      stop();

      start();

      write(0xa1);

      PORTB=read();

      stop();

      while (1)

            {

                 ;

            }

}