Atmega2560 Basic Course (5) - 8-bit timer (TIM0 / 2) timer interrupt

Atmega2560 Basic Course (5) - 8-bit timer (TIM0 / 2) timer interrupt

Atmega2560 a total of two 8-bit timers, timer 0, timer 2, so that a simple 8-bit timers in the timer interrupt requires three registers, TCNTx, TCCRxB, TIMSKx (x = 0,2), the timer 0 and 2 are basically the same structure, the following are an example timer 0

1. Works

TCNTx value of the timer increments up in value that is added to TOP 0XFF, interrupt flag. DETAILED TCNTx value is calculated as follows:

$\ Large \ n_ {First} = 2 ^ 8- (t_ {} * f_ {crystal when} / n_ {} division)$

Time units of the formula s, frequency hz, without conversion unit

2.TCNTx register

Starting 8-bit register, count

3.TCCRxB register

The main decision to divide the number of

DETAILED arranged as follows:

4.TIMSKx register

The main Enable interrupt

5. Specific examples of

Timer to 0, for example, you need a friend timer 2 can be replaced which register to use timer 2

/*
	定时器0，256分频，当中断发生时，PA0电平翻转
 */ 

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

float a=0.002;     //0.002s产生一次中断
int i=0;

int main(void)
{
	a=256-(F_CPU/256*a);        //计算初值
	i=a;                        //取整
	cli();
	DDRA|=_BV(DDA0);
	PORTA|=_BV(PA0);
	TCNT0=i;
	TCCR0B |=_BV(CS02);         //设定256分频
	TIMSK0 |=_BV(TOIE0);        //使能溢出中断
	sei();
	while (1)
	{
	}
}

ISR(TIMER0_OVF_vect){
	cli();
	TCNT0=i;
	PORTA^=(1<<PA0);
	sei();
}

Waveform chart