How are timer interrupts implemented in the AVR?

The AVR can be configured to execute interrupts if a timer event has occurred (the corresponding interrupt flag in the TIFRn is set). Normal program execution will be interrupted (almost) immediately and the processor will execute the code of the Interrupt Service Routine.

How do you stop a timer on AVR?

To stop the timer you have to clear the three bits CS10, CS11 and CS12. TCCR1B |= (0 << CS10); TCCR1B |= (0 << CS12); Those two lines has no effect on the register.

What is timer in AVR microcontroller?

A Timer is actually a counter that is increased every time when an instruction is executed. There are one to six timers in AVR Microcontrollers depending upon their family architecture. The AVR timers are of 8 bits and 16 bits.

Can timer be used as interrupt?

These are similar to external interrupts, but instead of firing on an external event, they fire on a timer. They are so called as they will intterupt the thread of execution after the current instruction completes, and run their code, returning to the next instruction from where it left off when it has finished.

What is timer interrupt in microcontroller?

For example, an interrupt occurs when a down counting timer reaches 0 and reloads the modulus in the main counter. The timer sends a hardware signal to an “interrupt controller” which suspends execution of the main program and makes the processor jump to a software function called an “interrupt service routine” or ISR.

What happens during a timer interrupt?

The timer interrupt handler runs the OS scheduler. If the process that was just interrupted has used up its time quantum, and there is some other runnable process, then the scheduler “returns” to that other process. (Later, when the timer interrupts some other process, the scheduler will “return” to this process).

What are the timer counter operation modes of the AVR?

In AVR, timers are of two types: 8-bit and 16-bit timers. In an 8-bit timer, the register used is 8-bit wide whereas in 16-bit timer, the register width is of 16 bits. This means that the 8-bit timer is capable of counting 2^8=256 steps from 0 to 255 as demonstrated below.

What is overflow interrupt?

Well, when the timer counter reaches its maximum value in bit – means that if the timer is a 8-bit timer, it can reaches maximum 255 – the timer go back to zero. At this specific moment, the timer overflow interrupt occur. This means that we can do something at the frequency that we want.

How many timers are there in AVR microcontroller?

In AVR ATmega16 / ATmega32, there are three timers: Timer0: 8-bit timer. Timer1: 16-bit timer. Timer2: 8-bit timer.

How are AVR delays calculated?

To calculate a delay, you need to calculate the cycle time and then count how may cycles you need to reach the wanted delay. In your case, 1MHz clock means 1000000 cycles per second. So 1 cycle equals 1/1000000 seconds or 1us .

What happens when a timer interrupt occurs?