CCS/MSP430F5529: WDT interrupt interval

So, if I wanted to implement this in C, I could do the following?

WDTIS = 6;

WDTSSEL = SMCLK;

This would make 2^9 = 512/1MHz = about 0.5 milliseconds.  I can't find very many examples of using this in C, so I just want to double check the syntax.

Actually it looks like I can use the ones defined in the header file like this:

WDTCTL = WDT_MRST_0_5;  // Set interval to 0.5ms

Oh, thank you, I see it now.  I am getting close to being done with it, I think.  For some reason my interrupt flag isn't being thrown, though.

#include <msp430.h>

volatile unsigned int i = 0;

int main(void)
{
    WDTCTL = WDTPW | WDTSSEL__SMCLK | WDTIS__512;  // WDT interval 0.5ms
    _EINT();                // enable interrupts
    SFRIE1 |= WDTIE;        // Enable WDT interrupt

    P4DIR |= BIT7;      // LED2 to output
    P4OUT &= ~BIT7;     // LED2 initially OFF

    P2DIR &= ~BIT1;     // set P2.1 as input (SW1)
    P2REN |= BIT1;      // enable pull-up resistor
    P2OUT |= BIT1;      // required for proper IO
    P2IE |= BIT1;       // enable interrupt at P2.1
    P2IES |= BIT1;      // enable hi->lo edge for interrupt
    P2IFG &= ~BIT1;     // clear any erroneous interrupt flag

    volatile unsigned int i = 0;

    while(1)    // Sit here and wait for interrupt
    {
        if(i >= 1000)
        {
            P2IFG |= BIT1;
            i = 0;
        }
    }
}

#pragma vector = WDT_VECTOR             //WDT ISR
__interrupt void watchdog_timer(void)
{
        i++;
}

#pragma vector = PORT2_VECTOR       //SW1 ISR
__interrupt void PORT2_ISR(void)
{
    P2IFG &= ~BIT1; // Clear the flag

    P4OUT ^= BIT7;  // Toggle LED2
}

The WDT ISR never happens, and i never increments.