GPTM Sample Programs

/* This program demonstrates the use of TimerA of Timer0

 * block to do a delay of the multiple of milliseconds.

   Because 16-bit mode is used, it will only work up to 4 ms.

*/

#include <stdint.h>

#include "inc/tm4c123gh6pm.h"

void timer0A_delayMs(int ttime);

void delayMs(int n);

int main (void)

{

    SYSCTL_RCGC2_R |= 0x00000020;   /* enable clock to GPIOF at clock gating control register */

    GPIO_PORTF_DIR_R = 0x0E;        /* enable the GPIO pins for the LED (PF3, 2 1) as output */

    GPIO_PORTF_DEN_R = 0x0E;        /* enable the GPIO pins for digital function */

    while(1) {

        GPIO_PORTF_DATA_R = 2;      /* turn on red LED */

        timer0A_delayMs(4);         /* Timer A msec delay */

        GPIO_PORTF_DATA_R = 0;      /* turn off red LED */

        delayMs(500);               /* use old delay function */

    }

}

/* millisecond delay using one-shot mode */

void timer0A_delayMs(int ttime)

{

    SYSCTL_RCGCTIMER_R |= 1;        /* (1). enable clock to Timer Block 0 */

    TIMER0_CTL_R = 0;               /* (2). disable Timer before initialization */

    TIMER0_CFG_R = 0x04;            /* (3). 16-bit option */

    TIMER0_TAMR_R = 0x01;           /* (4). one-shot mode and down-counter */

    TIMER0_TAILR_R = 16000 * ttime - 1; /* (5). Timer A interval load value register*/

    TIMER0_ICR_R = 0x1;             /* (6). clear the TimerA timeout flag*/

    TIMER0_CTL_R |= 0x01;           /* (7). enable Timer A after initialization*/

    while( (TIMER0_RIS_R & 0x1) == 0);  /* (8). wait for TimerA timeout flag to set*/

}

/* delay n milliseconds (16 MHz CPU clock) */

void delayMs(int n)

{

    int i, j;

    for(i = 0 ; i < n; i++)

        for(j = 0; j < 3180; j++)

            {}  /* do nothing for 1 ms */

}