Timer Delay

 * Created: 2016/08/22 04:02:04 PM
 *  Author: Kai
 This code is written in order to set up a manual delay function using the 16 bit counter TCNT1
 and its control registers TCCR1A and TCCR1B which is set accordingly to make the counter run in normal mode
 and count for 4 seconds.
 the bit 0x01 in the TIFR1 register is also used to indicate when the timer has reached overflow
 */


#include <avr/io.h>
#define F_CPU 16000000UL
#include <util/delay.h>

void to_delay (void);

int main(void)
{
    DDRB=0xff;      // outputs

    while(1)
    {
        PORTB = 0x20;       // sets pin 13 high
        to_delay();         // calls a function which manually delays the code by 4 seconds
        PORTB = 0x00;       // sets pin 13 low
        to_delay();         // again, calls the same function which manually delays the code by 4 seconds
    }
}

void to_delay (void){
    TCNT1 = 3026;           // presets the 16 bit counter to the decimal value of 3026 / 65536
    TCCR1A = 0;             // sets the control register to normal mode
    TCCR1B = 5;             // sets the prescale factor to 1024. This devides the clock input by 1024. this also starts the count
    while((TIFR1&0x01)==0); // holds this line of code until the counter reaches overflow
    TCNT1 = 0;              // clears the counter
    TIFR1 = 0x01;           // resets the flag bit in the TIFRn register. this is done by SETTING the TOVn bit
    }