MSP430F1611 timer capture mode

Here is a new approach where I am using CAOUT output (16kHz square wave ) generated from comparator to fed in to TA0
// MSP-FET430P140 Demo - Timer_A0, Capture of ACLK/8 using SMCLK
//
SMCLK = 1.07MHz
// MSP430F1611
// -----------------
// /|\|
// | |
// | P2.2/CAOUT|---+
// | | |
// | P1.1/TA0|<--+
// | |
// | P1.0|--->LED

//
//******************************************************************************

#include <msp430.h>
#include "msp430f1611.h"
unsigned int new_cap=0;
unsigned int old_cap=0;
unsigned int cap_diff=0;

unsigned int diff_array[16]; // RAM array for differences
unsigned int capture_array[16]; // RAM array for captures
unsigned char index=0;
unsigned char count = 0;

int main(void)
{
volatile unsigned int i;
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
//1.07MHz
BCSCTL1 = RSEL2;// RSEL=4(100)
DCOCTL = DCO1+DCO2;
P1DIR = 0x01; // Set P1.0 out,1.1 input dir
P1OUT &= ~0x01; // LED off
P1SEL = 0x02; // Set P1.1 to TA0
//P2DIR = 0x01; // P2.0-ACLK
//P2SEL |= 0x01;
//BCSCTL1 |= DIVA_3; // ACLK/8
P2DIR &= ~0x08; // P2.3 i/p direction
P2DIR |= 0x04; // P2.2 0/p direction
P1DIR |= 0x10; // P1.4 output SMCLK
P2SEL |= 0x0C; // CA0 select, caout
P1SEL |= 0x10; // SMCLK output P1.4

//comparator
CACTL1 = CARSEL+CAREF_2; // Comp. A Int. Ref. enable on CA1
// Comp. A Int. Ref. Select 2 : 0.5*Vcc
CACTL2 = P2CA0+CAF+CAOUT; // Comp. A Connect External Signal to CA0
// Comp. A Enable Output Filte
CACTL1 |= CAON;
CACTL1 |= CAON+CAIE ;


//Timer

CCTL0 = CM_1 + SCS + CCIS_0 + CAP + CCIE; // Rising edge + CCI0A (P1.1)
// + Capture Mode + Interrupt

TACTL = TASSEL_2 + MC_2; // SMCLK + Continuous Mode

__bis_SR_register(LPM0_bits + GIE); // LPM0 + Enable global ints
}

#pragma vector=TIMERA0_VECTOR
__interrupt void TimerA0(void)
{
new_cap = TACCR0;
cap_diff = new_cap - old_cap;

diff_array[index] = cap_diff; // record difference to RAM array
capture_array[index++] = new_cap;
if (index == 16)
{
index = 0;
P1OUT ^= 0x01; // Toggle P1.0 using exclusive-OR
}
old_cap = new_cap; // store this capture value
count ++;
if (count == 32)
{
count = 0;
__no_operation(); // SET BREAKPOINT HERE
}

}

count in ISR never reaches 32. I am not sure how to calculate the the frequency as 16kHz with diff_array which is 0 all the time.

You set CAIE. But I don’t see a comparator ISR in your code. If there is none, then as soon as the comparator triggers, the MSP resets (the comparator interrupt has a higher priority than the TimerA interrupt, so it is granted first - and jumps into the void, eventually resetting the MSP.

All the global data/variables you access from ISR, shall be volatile. Does count reaches, let' s say 2? Are you sure your ISR is fired at least one time?