/*  p5_2.c: Toggle PF1 LED every 1second using the SysTick Counter */

/* This program sets up the SysTick to set the COUNT flag at 1 Hz.  The system clock is running at 16 MHz.
  1sec / 62.5ns = 16,000,000 for RELOAD register.
  The program then polls the flag and toggles the red LED PORTF1 every time COUNT flag is set.
  The COUNT flag is cleared when the STCTRL register is read. */


#include "TM4C123GH6PM.h"

int main (void)
{
    /* enable clock to GPIOF at clock gating control register */
    SYSCTL->RCGCGPIO |= 0x20;
    /* enable the GPIO pins for the LED (PF3, 2 1) as output */
    GPIOF->DIR = 0x0E;
    /* enable the GPIO pins for digital function */
    GPIOF->DEN = 0x0E;
    
    /* Configure SysTick */
    SysTick->LOAD = 16000000 - 1; /* reload with number of clocks per second */
    SysTick->CTRL = 5;     /* enable it, no interrupt, use system clock */

    while (1)
    {
        if (SysTick->CTRL & 0x10000) /* if COUNT (D16 of CTRL reg.) flag is set */
            GPIOF->DATA ^= 2;    /* toggle PORTF1 red LED */
    }
}

/* This function is called by the startup assembly code to perform system specific initialization tasks.*/
void SystemInit(void)
{
    __disable_irq();    /* disable all IRQs */
    
    /* Grant coprocessor access */
    /* This is required since TM4C123G has a floating point coprocessor */
    SCB->CPACR |= 0x00F00000;
}