Question

2. Timer0 is an 8-bit timer. Configure the timer in normal mode (counts from 0x00 to 0xFF and rolls over), use CS02:C800=001 (CikI/O = 16 Mhz) for enabling the counter. Write a program to count the number of times Timer overflowed after enabling the counter.

I am using the ATmega328P only. please do NOT use any other microprocessor.

Answer 1

Answer:

Programming steps :

1. Intialize TNCNT0 to value 0.

2. Program prescalar by setting CS bits of TCCR0.

3. Set Timer Overflow Interrupt TOIE0 bit of TIMSK register.

4. Enable global interrupt by sei() command.

5. write code for ISR function with vector name TIMER_OVF_vect.

ATmega168/328 Code:

CODE 1:

// this code sets up a timer0 for 1ms @ 16Mhz clock cycle
// in order to function as a time delay at the beginning of the main loop
// using no interrupts


#include <avr/io.h>


int main(void)
{

   while (1)
   {

        // Set the Timer Mode to CTC
        TCCR0A |= (1 << WGM01);

        // Set the value that you want to count to
        OCR0A = 0xF9;

        // start the timer

       TCCR0B |= (1 << CS01) | (1 << CS00);
       // set prescaler to 64 and start the timer

        while ( (TIFR0 & (1 << TOV0) ) > 0)     // wait for the overflow event
        {
       }
        
        TIFR0 |= (1 << TOV0);
        // reset the overflow flag

    }
}

CODE 2:

// this code sets up a timer0 for 4ms @ 16Mhz clock cycle

// an interrupt is triggered each time the interval occurs.

#include <avr/io.h>

#include <avr/interrupt.h>

int main(void)
{

        // Set the Timer Mode to CTC
        TCCR0A |= (1 << WGM01);

        // Set the value that you want to count to
        OCR0A = 0xF9;

        TIMSK0 |= (1 << OCIE0A); //Set the ISR COMPA vect

        sei();   //enable interrupts

       TCCR0B |= (1 << CS02);
       // set prescaler to 256 and start the timer

while (1)
{

               // main loop
}

}

ISR (TIMER0_COMPA_vect)   // timer0 overflow interrupt

{

// event to be executed every 4ms here

}