sbit IO   = P3^4;
sbit SCLK = P3^3;
sbit RSTB = P3^5;
/***************************************************************************/
/* Prototypes                                                              */
/***************************************************************************/
uchar    rt_rbyte();
void    rt_reset();
void    rt_wbyte(uchar);
void    get_time(time *tm);
void    set_time(time *tm);
/* ----------------------------------------------------------------------- */
void rt_reset()
{
   SCLK = 0;
   RSTB = 0;
   RSTB = 1;
}
/* ----------------------------------------------------------------------- */
void rt_wbyte(uchar W_Byte)
{
    uchar i;
    for(i = 0; i < 8; ++i)
    {
        IO = 0;
        if(W_Byte & 0x01)
        {
            IO = 1;    /* set port pin high to read data */
        }
        SCLK = 0;
        SCLK = 1;
        W_Byte >>= 1;
      }
}
/* ----------------------------------------------------------------------- */
uchar rt_rbyte()
{
    uchar i;
    uchar R_Byte;
    R_Byte = 0x00;
    IO = 1;
    for(i=0; i<8; ++i)
    {
        R_Byte >>= 1;
        SCLK = 1;
        SCLK = 0;
        if(IO){
            R_Byte |= 0x80;
        }
    }
    return R_Byte;
}
/* ----------------------------------------- */
void get_time(time *tm)
{
    rt_reset();
    rt_wbyte(0xbf);    /* clock burst read (eight registers) */
    tm->sec = rt_rbyte();
    tm->min = rt_rbyte();
    tm->hour = rt_rbyte();
    tm->day = rt_rbyte();    //date
    tm->month = rt_rbyte();
    tm->year = rt_rbyte();        //day
    tm->year = rt_rbyte();
    rt_rbyte();        /* must read control register in 
burst mode */
    rt_reset();
    RSTB = 0;
}
/* ----------------------------------------- */
void set_time(time *tm)
{
    rt_reset();
    rt_wbyte(0x8e);    /* control register */
    rt_wbyte(0);        /* disable write protect */
    rt_reset();
    rt_wbyte(0x90);    /* trickle charger register */
    rt_wbyte(0xab);    /* enable, 2 diodes, 8K resistor */
    rt_reset();
    rt_wbyte(0xbe);    /* clock burst write (eight registers) */
    rt_wbyte(tm->sec);
    rt_wbyte(tm->min);
    rt_wbyte(tm->hour);
    rt_wbyte(tm->day);    //date
    rt_wbyte(tm->month);
    rt_wbyte(1);        //day
    rt_wbyte(tm->year);
    rt_wbyte(0x80);        /* must write control register in 
burst mode, enable write protect*/
    rt_reset();
    RSTB = 0;
}