/* p5_7.c Toggling blue LED using TPM0 delay

 * This program uses TPM0 to generate long delay to
 * toggle the blue LED.
 * MCGIRCLK (32.768 kHz) is used as timer counter clock.
 * Prescaler is set to divided by 4 and the Modulo register
 * is set to 40,959. The timer counter overflows at
 * 32,768 Hz / 40,960 / 4 = 0.2 Hz
 * 
 * The blue LED is connected to PTD1.
 */

#include <MKL25Z4.H>

int main (void) {
    SIM->SCGC5 |= 0x1000;       /* enable clock to Port D */
    PORTD->PCR[1] = 0x100;      /* make PTD1 pin as GPIO */
    PTD->PDDR |= 0x02;          /* make PTD1 as output pin */
    
    SIM->SCGC6 |= 0x01000000;   /* enable clock to TPM0 */
    SIM->SOPT2 |= 0x03000000;   /* use MCGIRCLK as timer counter clock */
    
    TPM0->SC = 0;               /* disable timer while configuring */
    TPM0->SC = 0x02;            /* prescaler /4 */
    TPM0->MOD = 40960 - 1;      /* modulo value */
    TPM0->SC |= 0x80;           /* clear TOF */
    TPM0->SC |= 0x08;           /* enable timer free-running mode */
    
    while (1) {
        while((TPM0->SC & 0x80) == 0) { } /* wait until the TOF is set */
        TPM0->SC |= 0x80;       /* clear TOF */
        PTD->PTOR = 0x02;       /* toggle blue LED */
    }
}