/* www.microDigitalEd.com
 * p6_6.c Toggling red LED at 1 Hz using Timer_A1 interrupt
 * System clock running at 3 MHz is used. Timer_A1 is configured
 * to count up from 0 to 46,875-1, which is loaded in TIMER_A1->CCR[0].
 * When the counter (TA1R) value reaches TIMER_A1->CCR[0], CCIFG 
 * bit in TIMER_A1->CCTL[0] is set and an interrupt is generated.
 * The clock input dividers are set to divide by 8 and 8.
 * The timer counter roll over interval is: 3,000,000 / 8 / 8 / 46,875 = 1 Hz.
 * In the interrupt handler, the red LED is toggled.
 * The red LED is connected to P2.0.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0.
 */
#include "msp.h"

int main(void) 
{
    __disable_irq();

    /* initialize P2.0 for red LED */
    P2->SEL1 &= ~1;         /* configure P2.0 as simple I/O */
    P2->SEL0 &= ~1;
    P2->DIR |= 1;           /* P2.0 set as output */

    TIMER_A1->CTL = 0x02D1;         /* SMCLK, ID=/8, up mode, TA clear */
    TIMER_A1->CCR[0] = 46875 -1;     /* for 1 sec */
    TIMER_A1->EX0 = 7;              /* IDEX = /8 */
    TIMER_A1->CCTL[0] |= 0x10;      /* enable TA1.0 interrupt */

    NVIC_SetPriority(TA1_0_IRQn, 3);    /* set priority to 3 in NVIC */
    NVIC_EnableIRQ(TA1_0_IRQn);         /* enable interrupt in NVIC */
    __enable_irq();                     /* global enable IRQs */   

    while (1) {
    }
}

void TA1_0_IRQHandler(void) 
{
    TIMER_A1->CCTL[0] &= ~1;    /* clear interrupt flag */
    P2->OUT ^= 1;               /* toggle red LED */
}