unsigned char twi_get_last_status(void)
{
return (TWSR & (1 << TWS7|1 << TWS6|1 << TWS5|1 << TWS4|1 << TWS3));
}
//---------------------------------------------------------------------------
unsigned char twi_Wait_TWINT(void)
{
   register unsigned char i=0;
  //ожидаем TWIN==1
   do
    {
     if(TWCR & (1<<TWINT))
      return 0x01;  //true
    }
   while(--i);
   return 0x00;  //false
}
//---------------------------------------------------------------------------
void twi_init_asmaster(void)
{
  TWBR = 0x20;
  TWSR = (0 << TWPS1|0 << TWPS0);
  TWCR |= (1 << TWEN|1 << TWEA);
  
  twi_start();
  twi_write_address(0xff, 'r');
  twi_start();
  twi_stop();
}
//---------------------------------------------------------------------------
unsigned char twi_start(void) //он же повстарт
{
  TWCR = (1 << TWINT|1 << TWSTA|1 << TWEN);
  unsigned char twi_last_status = twi_get_last_status();
  if(twi_Wait_TWINT() == 0x01)
   {
    if((twi_last_status == 0x08) || (twi_last_status == 0x10))
     return 0x01;  //true
   }
  else
   return 0x00; //false
  return 0;
}
//---------------------------------------------------------------------------
unsigned char twi_stop(void)
{
  TWCR = (1 << TWINT|1 << TWSTO|1 << TWEN);
  register unsigned char i=0;
  do
   {
    if(PINC & 0x10) //смотрим, установилась ли в "1" линия SDA
     return 0x01;  //true
   }
  while(--i);
  TWCR = (1 << TWINT|1 << TWSTO);  
  return 0x00;  //false
}
//---------------------------------------------------------------------------
unsigned char twi_write_byte(unsigned char data_byte)
{
  TWDR = data_byte;
  TWCR = (1 << TWINT|1 << TWEN);
  if(twi_Wait_TWINT() == 0x01)
   {
    unsigned char twi_last_status = twi_get_last_status();
    if((twi_last_status == 0x28) || (twi_last_status == 0x30))
     return 0x01;  //true
    else if(twi_get_last_status() == 0x38)
     return 0x00; //потеряли приоритет
   }
  else
   return 0x00; //false
  return 0;
}
//---------------------------------------------------------------------------
unsigned char twi_write_address(unsigned char address_byte, char read_write)
{
  if(read_write == 'r')
   address_byte |= 0x01;
  else if(read_write == 'w')
   address_byte &= 0xFE;
  else
   return 0x00;
  TWDR = address_byte;
  TWCR = (1 << TWINT|1 << TWEN);
  if(twi_Wait_TWINT() == 0x01)
   {
    unsigned char twi_last_status = twi_get_last_status();
    if(read_write == 'w')
     {
      if((twi_last_status == 0x18) || (twi_last_status == 0x20))
       return 0x01;  //true
      else if(twi_get_last_status() == 0x38)
       return 0x00; //потеряли приоритет
     }
    else if(read_write == 'r')
     {
      if((twi_last_status == 0x40) || (twi_last_status == 0x48))
       {
       TWCR = (1 << TWINT|1 << TWEA|1 << TWEN);
        return 0x01;  //true
       }
      else if(twi_get_last_status() == 0x38)
       return 0x00; //потеряли приоритет
     }
   }
  else
   return 0x00; //false
  return 0;
}
//---------------------------------------------------------------------------
unsigned char twi_read_byte(unsigned char *data, unsigned char ack_nack) //ack_nack == 1 - подтверждение
{                                                                       //ack_nack == 0 - неподтверждение
  if(twi_Wait_TWINT() == 0x01)
   {
    unsigned char twi_last_status = twi_get_last_status();
    if((twi_last_status == 0x50) || (twi_last_status == 0x58))
     {
      *data = TWDR;
      if(ack_nack == 1) TWCR = (1 << TWINT|1 << TWEA|1 << TWEN);
      if(ack_nack == 0) TWCR = (1 << TWINT|1 << TWEN);
       return 0x01;  //true
     }
    }
   else
    return 0x00;
  return 0;
}

void ADT75_init(void)
{
twi_start();
twi_write_address(0x90, 'w');
twi_write_byte(0x01);
twi_write_byte(0x20);
twi_stop();
}
//---------------------------------------------------------------------------
void ADT75_start(void)
{
twi_start();
twi_write_address(0x90, 'w');
twi_write_byte(0x04);
twi_stop();
}
//---------------------------------------------------------------------------
char ADT75_read(void)
{
unsigned char read_temp_h = 0;
unsigned char read_temp_l = 0;
twi_start();
twi_write_address(0x90,'w');
twi_write_byte(0x00);
twi_stop();
twi_start();
twi_write_address(0x90, 'r');
twi_read_byte(&read_temp_h, 1);
twi_read_byte(&read_temp_l, 0);
twi_stop();
return (char)read_temp_h;
}

      if(ack_nack == 1) TWCR = (1 << TWINT|1 << TWEA|1 << TWEN);
      else TWCR = (1 << TWINT|1 << TWEN);

      TWCR = (ack_nack == 1) ? (1 << TWINT|1 << TWEA|1 << TWEN) : (1 << TWINT|1 << TWEN);

    uint8_t temp = (1 << TWINT|1 << TWEN);
    if(ack_nack == 1) temp |= (1 << TWEA);
    TWCR = temp;

    
while ( 1 )
    {
        // send START condition
        TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);

        // wait until transmission completed
        while(!(TWCR & (1<<TWINT)));

        // check value of TWI Status Register. Mask prescaler bits.
        twst = TW_STATUS & 0xF8;

        if ( (twst != TW_START) && (twst != TW_REP_START)) continue;
....
}

    if( twst != TW_MT_DATA_ACK) return 1;
    return 0;

   unsigned char twi_last_status = twi_get_last_status();
    if(read_write == 'w')
     {
      if((twi_last_status == 0x18) || (twi_last_status == 0x20))
       return 0x01;  //true
      else if(twi_get_last_status() == 0x38)
       return 0x00; //потеряли приоритет
     }
....

twst = TW_STATUS & 0xF8;
if( twst != TW_MT_DATA_ACK) return 1;

#define TW_STATUS_MASK        (_BV(TWS7)|_BV(TWS6)|_BV(TWS5)|_BV(TWS4)|\
                _BV(TWS3))
#define TW_STATUS        (TWSR & TW_STATUS_MASK)

for(;;)
  {
   set_conG;
   for(int i = 0; i < 20; i++)
    _delay_loop_2(0xFFFF);
   ds1621_start();
   clr_conG;
   for(int i = 0; i < 20; i++)
    _delay_loop_2(0xFFFF);
   temperature = ds1621_read();
  }