Problem with USCB I2C and no acknowledge

Hi,

on my board I use a MSP430F5419A with UCB0 for I2C interface. With the following init:

void iic_init(void)
{
	UCB0CTL1 = UCSWRST;							// Enable SW Reset
	UCB0CTL0 = 0x0f;							// I2C Master, synchronous mode
	UCB0CTL1 |= 0x80;							// use SMClk
	UCB0BR0 = 10;								// fSCL = SMCLK/12 = ~100kHz
	UCB0BR1 = 0;
	UCB0IE = 0;
	UCB0CTL1 &= ~UCSWRST;						// Clear SW reset
}

My byte write function looks like this:

bool iic_byte_write(uchar sladr, ushort adr, uchar data, uchar adrlen)
{
	UCB0CTL1 |= UCTR;							// Transmitter

	UCB0I2CSA = sladr >> 1;						// Adresse ohne R/W Bit
	UCB0CTL1 |= UCTXSTT;						// Start Condition

	while (!(UCB0IFG & UCTXIFG));				// Dev Adr gesendet

	if (!(UCB0IFG & UCNACKIFG))					// Ack empfangen
	{
		if (adrlen == 8)
			UCB0TXBUF = adr & 0xff;
		else
			UCB0TXBUF = (adr >> 8) & 0xff;
		while (!(UCB0IFG & UCTXIFG));				// Reg Adr gesendet
		if (!(UCB0IFG & UCNACKIFG))					// Ack empfangen
		{
			if (adrlen == 16)
			{
				UCB0TXBUF = adr & 0xff;
				while (!(UCB0IFG & UCTXIFG));		// Reg Adr gesendet
				if (UCB0IFG & UCNACKIFG)			// Ack nicht empfangen
				{
					UCB0CTL1 |= UCTXSTP;
					return(FALSE);
				}
			}
			UCB0TXBUF = data;						// Datum senden
			while (!(UCB0IFG & UCTXIFG));			// Datum gesendet
			if (!(UCB0IFG & UCNACKIFG))				// Ack empfangen
			{
				UCB0CTL1 |= UCTXSTP;
				return(TRUE);
			}
		}
	}

	UCB0CTL1 |= UCTXSTP;
	return(FALSE);
}

My problem is If I write to a device which is not on the bus the program will hang up. How can I break the function if I don't receive the acknowledge after the device adress?

Thank you for your help.

br

martin sauer