51和AVR单片机模拟I2C的区别？

只看该作者 · 2007-4-12 21:56

感觉AVR的IO模拟I2C和51模拟还是有区别的，下面是AVR和51的模拟I2C的例子。小弟现在有点迷惑，那位达人能解释一下？
/***********************AVR
unsigned char I2C_Read(unsigned char bEnd)
{
     unsigned char i,mb;

     Set_SDA;     //release sda line
     mb=0;
     for(i=0;i<8;i++)
     {
         mb=mb<<1;

         I2C_Delay();
         Set_SCL;
         I2C_Delay();
         if( SDA_High ) mb++;
         I2C_Delay();
         Cls_SCL;
         if(i!=7)         I2C_Delay();
     }
     if( bEnd )       Set_SDA;         //end read
     else             Cls_SDA;         //ack
     I2C_Delay();

     Set_SCL;
     I2C_Delay();
     Cls_SCL;
     I2C_Delay();
     Set_SDA;

     return mb;

}
////////////////////////51
unsigned char I2C_Read()
{
    unsigned char dat;
    unsigned char t = 8;
    I2C_SDA = 1;    //在读取数据之前，要把SDA拉高，使之处于输入状态
    do
    {
        I2C_SCL = 1;    I2C_Delay();
        dat <<= 1;
        if ( I2C_SDA ) dat++;
        I2C_SCL = 0;    I2C_Delay();
    } while ( --t != 0 );
    return dat;
}