Halting the clocks while debugging

My system does not halt the micro while debugging, so when I debug, I always enter into the ISR.  Why wont the Clock halt?

Timer Setup:

// Timer T0_B3 init
TB0CCR0 = 99999;
TB0CTL = TBSSEL_2 + MC_1; // SMCLK, UP mode
TB0CCTL0 = CCIE; // TBCCR0 interrupt enabled

ISR:
#pragma vector=TIMER0_B0_VECTOR

__interrupt void TIMER0_B0_ISR_HOOK(void){
g_time_msec++;
}

Setup