/* www.microDigitalEd.com
 * p5_8.c Toggling red LED at 1 Hz using Timer_A
 *
 * This program uses Timer_A to generate 1 second delay to
 * toggle the red LED.
 * Subsystem Master Clock (SMCLK) running at 3 MHz is used. 
 * Timer_A 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], the CCIFG 
 * bit in TIMER_A1->CCTL[0] is set.
 * 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.
 * The red LED is connected to P2.0.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0
 * on XMS432P401R Rev C.
 */

#include "msp.h"

int main(void) {
    /* 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->EX0 = 7;          /* IDEX = /8 */
    TIMER_A1->CCR[0] = 46875 - 1;   /* for 1 sec */

    while (1) {
        while((TIMER_A1->CCTL[0] & 1) == 0);    /* wait until the CCIFG is set */
        TIMER_A1->CCTL[0] &= ~1;                /* clear interrupt flag */
        P2->OUT ^= 1;                           /* toggle red LED */
    }
}