/* p5_4.c Toggling blue LED using TPM0 delay

 This program uses TPM0 to generate maximal delay to toggle the blue LED.
 MCGFLLCLK (41.94 MHz) is used as timer counter clock.
 The Modulo register is set to 65,535. The timer counter overflows at
 41.94 MHz / 65,536 = 640 Hz
 We put the time out delay in a for loop and repeat it for 320 times before we toggle the LED. This results in the LED flashing at half second on and half second off.
 The blue LED is connected to PTD1.
 */

#include <MKL25Z4.H>

int main (void) {
    int i;
    
    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 |= 0x01000000;   /* use MCGFLLCLK as timer counter clock */
    
    TPM0->SC = 0;               /* disable timer while configuring */
    TPM0->MOD = 0xFFFF;         /* max modulo value */
    TPM0->SC |= 0x80;           /* clear TOF */
    TPM0->SC |= 0x08;           /* enable timer free-running mode */
    
    while (1) {
        for(i = 0; i < 320; i++) {  /* repeat timeout for 320 times */
            while((TPM0->SC & 0x80) == 0) { }/* wait until the TOF is set */
            TPM0->SC |= 0x80;   /* clear TOF */
        }
        PTD->PTOR = 0x02;       /* toggle blue LED */
    }
}