DS1820 auf AT89C2051

Sodala ich hab einen AT89C2051 mit dem DS1820 verbunden, leider hängt 
das Programm bei der
while (ReadByte()==0xff); // wait for conversion complete
Zeile im ReadTemp UP.

Hat jemand einen Plan?



sbit DQ  =  P1^3;  // connect with DS1820 Data pin

//---------------------------------------
// Delay mS function
//---------------------------------------
void DelayMs(unsigned int count)
{  // mSec Delay 11.0592 Mhz
    unsigned int i;               // Keil v7.5a
    while(count) {
        i = 115;
    while(i>0) i--;
        count--;
    }
}


//----------------------------------------
// DELAY at 11.0592MHz crystal.
// Calling the routine takes about 22us, and then
// each count takes another 17us.
// test with KEIL C51 V7.5
//----------------------------------------
void DelayUs(int us)
{
  int i;
  for (i=0; i<us; i++);
}

//----------------------------------------
// Reset DS1820
//----------------------------------------
bit ResetDS1820(void)
{
  bit presence;
  DQ = 0;     //pull DQ line low
  DelayUs(29);   // leave it low for about 490us
  DQ = 1;     // allow line to return high
  DelayUs(3);   // wait for presence 55 uS
  presence = DQ;   // get presence signal
  DelayUs(25);   // wait for end of timeslot 316 uS
  return(presence); // presence signal returned
}   // 0=presence, 1 = no part

//-----------------------------------------
// Read one bit from DS1820
//-----------------------------------------
bit ReadBit(void)
{
  unsigned char i=0;
  DQ = 0;   // pull DQ low to start timeslot
  DQ=1;
  for (i=0; i<3; i++); // delay 17 us from start of timeslot
  return(DQ); // return value of DQ line
}

//-----------------------------------------
// Write one bit to DS1820
//-----------------------------------------
void WriteBit(bit Dbit)
{
  unsigned char i=0;
    DQ=0;
  DQ = Dbit ? 1:0;
  DelayUs(5);       // delay about 39 uS
  DQ = 1;
}

//-----------------------------------------
// Read 1 byte from DS1820
//-----------------------------------------
unsigned char ReadByte(void)
{
  unsigned char i;
  unsigned char Din = 0;
  for (i=0;i<8;i++)
  {
    Din|=ReadBit()? 0x01<<i:Din;
    DelayUs(6);
  }
  return(Din);
}

//-----------------------------------------
// Write 1 byte
//-----------------------------------------
void WriteByte(unsigned char Dout)
{
  unsigned char i;
  for (i=0; i<8; i++) // writes byte, one bit at a time
  {
    WriteBit((bit)(Dout & 0x1));     // write bit in temp into
    Dout = Dout >> 1;
  }
  DelayUs(5);
}

//-----------------------------------------
// Read temperature
//-----------------------------------------
void ReadTemp(unsigned char * buff)
{
  unsigned char n;

    EA=0;  // disable all interrupt
     ResetDS1820();
    WriteByte(0xcc);  // skip ROM
    WriteByte(0x44);  // perform temperature conversion
    while (ReadByte()==0xff); // wait for conversion complete
    ResetDS1820();
    WriteByte(0xcc);  // skip ROM
    WriteByte(0xbe);  // read the result

    for (n=0; n<9; n++)     // read 9 bytes but, use only one byte
    {
       buff[n]=ReadByte();  // read DS1820
    }
  EA=1;
}