Communication with apple coprocessor over I2C

Dear All,

I am working with MSP430F5438A microcontroller and apple authentication co-processor V2.0C. I have followed all hardware requirements mentioned in documentation provided by apple. I am using following code for initializing I2C (my CPU frequency is 20MHz)

void halI2CB3Init(void)
{
  unsigned short timeout = 20000;
  unsigned char temploop=0;

  UCB3SDA_SEL |= UCB3SDA_PIN;
  UCB3SCL_SEL |= UCB3SCL_PIN;
  //DIR Registers are don't cares
  UCB3SDA_DIR |= UCB3SDA_PIN;
  UCB3SCL_DIR |= UCB3SCL_PIN;

  UCB3CTL1 |= UCSWRST;                      // Enable SW reset
  UCB3CTL0 = UCMST + UCMODE_3 + UCSYNC;     // I2C Master, synchronous mode
  UCB3CTL1 = UCSSEL_2 + UCSWRST;            // Use SMCLK
  UCB3BR0 = 200;//50;//62;//45;                             // fSCL = SMCLK/45 = ~400kHz
  UCB3BR1 = 0;
  UCB3CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation

  //Generate STOP condition at least 9 times to make sure that the slave will release the bus at MCU power up.
  for(temploop=9;temploop>0;temploop--)
  {
    UCB3SDA_OUT &= ~UCB3SDA_PIN;            // SCL 0
    UCB3SCL_OUT &= ~UCB3SCL_PIN;            // SDA 0
    UCB3SDA_OUT |= UCB3SDA_PIN;             // SCL 1
    UCB3SCL_OUT |= UCB3SCL_PIN;             // SDA 1
  }


  UCB3SDA_OUT |= UCB3SDA_PIN;
  UCB3SCL_OUT |= UCB3SCL_PIN;
  AUTH_RST_OUT |= AUTH_RST_PIN;
  AUTH_RST_OUT &= ~AUTH_RST_PIN;
  __delay_cycles((unsigned long) 18 * 15);
  AUTH_RST_OUT |= AUTH_RST_PIN;

  while((UCB3STAT & UCBBUSY) && (--timeout > 0)); //PRC 15MAY - added

}

But I am not getting ACK from apple co-processor when I write slave address, for doing so I am using following code-

unsigned char halI2CB3SendSlaveAddress(enum halI2Copt read)
{
  unsigned char brkflag=1, lap=0;
  unsigned short timeout = 20000;

  while(brkflag)
  {
    // Ready the 7bit address
    UCB3I2CSA = auth_i2c_address;
    UCB3CTL0 &= ~UCSLA10;
    // Transmit flag
   
      UCB3CTL1 |=  UCTR;
    // Send Start Condition
    UCB3CTL1 |= UCTXSTT;
    {
      // Wait for ACK or NACK after Slave Address
      while ((UCB3CTL1 & UCTXSTT) && (--timeout > 0));
      if(UCB3IFG & UCNACKIFG)
      {
        __delay_cycles((unsigned long) 18 * 600); //600 usec delay
//        __delay_cycles((unsigned long) 18 * 5000); //PRC 5SEP12 - 5000 usec delay //Not working.

        timeout=20000;
        ++lap;
        if(temp_lap < lap)
        {
          DEBUG_PRINTF(DEBUG_CP,"T:S2:%d~",lap);
          return 2;// return failure since ACK not received.
        }
      }
      else
        brkflag=0;
    }
  }
  return 0;// Ack received
}

Can anyone help me with what went wrong here?

My function always returns 2 here.

Thanks in advance,

Sharadanand Karanjkar