MSP430F67691 - Timer A Issue

Other Parts Discussed in Thread: MSP430F67691, MSP430F47176

I am currently migrating my code from MSP430F47176 to MSP430F67691. I have one timer (TIMER A0) that counts up to one configurable value (TACCR) using ACLK (32 kHz) as source. I use interrupt routine every time the timer reach this value, enabling interrupts and initiating timer again. My source clock configuration is:

- ACLK: 32 kHZ

- MCLK, SMCLK: 16 MHz

void xtal_init(void)
{
	//UCSCTL3 |= SELREF__XT1CLK;		// FLL Ref = REFO
	UCSCTL4 = SELA_0 + SELS_4 + SELM_4;       // Select ACLK = LFXT1
	                                          //       SMCLK = DCO
	                                          //        MCLK = DCO

	// Initialize LFXT1
	//P7SEL |= 0x03;                            // Select XT1
	UCSCTL6 &= ~(XT1OFF);                     // XT1 On
	UCSCTL6 |= XCAP_3;                        // Internal load cap

	// Loop until XT1 fault flag is cleared
	do
	{
		UCSCTL7 &= ~XT1LFOFFG;                  // Clear XT1 fault flags
	}while (UCSCTL7&XT1LFOFFG);               // Test XT1 fault flag

	// Initialize DCO to 16,777216MHz
	__bis_SR_register(SCG0); 	// Disable the FLL control loop
	UCSCTL0 = 0x0000;			// Set lowest possible DCOx, MODx
	UCSCTL1 = DCORSEL_5;		// Select DCO range 24MHz operation
	UCSCTL2 = FLLD_1 + FLLD_16MHz;// Set DCO Multiplier for 16,777216MHz
	                            // (N + 1) * FLLRef = Fdco
	                            // (511 + 1) * 32768 = 16,777216MHz
	                            // Set FLL Div = fDCOCLK/2
	__bic_SR_register(SCG0);    // Enable the FLL control loop

	// Worst-case settling time for the DCO when the DCO range bits have been
	// changed is n x 32 x 32 x f_MCLK / f_FLL_reference. See UCS chapter in 5xx
	// UG for optimization.
	// 32 x 32 x 16,777216 MHz / 32,768 Hz = 524288 = MCLK cycles for DCO to settle
	__delay_cycles(524288);//

	// Loop until XT1,XT2 & DCO stabilizes
	do
	{
		UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);
	                                          // Clear XT2,XT1,DCO fault flags
	    SFRIFG1 &= ~OFIFG;                    // Clear fault flags
	}while (SFRIFG1&OFIFG);                   // Test oscillator fault flag

}

Problem I have found is that, while I debug, timer seems to count much faster than expected. I know it because I have checked that TIMER REGISTER counts about 5000 every I debug only ONE instruction. The same code in my old MSP430F47176 works perfectly I have to execute several instructions just to count 1.

This is timer initialization and interrupt service routine:

void TimerA0_init(void)
{
	TA0CTL = TACLR;

	TA0CCR0 = (Uint16) 32*50*CHECK_RX_RATE-1;

	TA0CCTL0 = 0x00;
	TA0CCTL1 = 0x00;
	TA0CTL = TASSEL_1 + MC_1 + TAIE; //source: ACLK - 32 kHz; Count UP to TACCR0
}

// Timer A0 interrupt service routine
#pragma vector=TIMER0_A1_VECTOR
__interrupt void Timer_A (void)
{
	__bis_SR_register(GIE); //Interrupts enabled

	//stop timer
	TA0CTL = TACLR; //Reset & Switch Off TA
	TA0CTL = 0;

	TA0CCR0 = (Uint16) 32*50*CHECK_RX_RATE-1;

	TA0CCTL0 = 0x00;
	TA0CCTL1 = 0x00;
	TA0CTL = TASSEL_1 + MC_1 + TAIE; //source: ACLK - 32 kHz; Count UP to TACCR0
}

I execute it in loop while (1); 

First thing I thought was that perhaps source ACLK was not correxctly configured, but I have checked ACLK PIN of microcontroller and is 32 kHz, as expected.

Thank you.