Useful tips

# What is the resolution of TIMER1 in atmega8?

## What is the resolution of TIMER1 in atmega8?

This is known as the resolution of the timer (ie 8 bit timer, 16 bit timer). In an 8 bit timer, the register is 8 bits long and thus can store a number from 0 to 255. Likewise, a 16 bit timer can hold a value between 0 to 65535.

### What is the maximum value of TIMER1 in Atmega 8535?

Since TIMER1 is a 16-bit timer, it can count upto a maximum of 65535.

What triggers a timer counter 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.

What is an AVR timer?

A timer is a simple counter! The input clock of microcontroller and operation of the timer is independent of the program execution. All the Atmel microcontrollers have Timers as an inbuilt peripheral. Timers can run asynchronous to the main AVR core hence timers are totally independent of CPU.

## What is TCNT0?

TCNT0 is the counter register for Timer/counter 0. In the example above it increases every CLK/64 tick He’s most probably sat down with a pen and a piece of paper (and a calculator) to find/get to the “magic” numbers 186 and 208. TCCR1A and TCCR1B are different registers, but they work on the same timer, timer1.

### Why do we need prescaler in AVR?

We can choose 256 if we need the timer for a greater duration elsewhere. Thus, we always choose prescaler which gives the counter value within the feasible limit (255 or 65535) and the counter value should always be an integer.

What is the largest time delay TIMER1 can generate?

At this frequency, and using a 16-bit timer (MAX = 65535), the maximum delay is 4.096 ms. It’s quite low.

What is CTC mode?

In CTC mode the counter is cleared to zero when the counter value (TCNT2) matches the OCR2A. The OCR2A defines the top value for the counter, hence also its resolution. This mode allows greater control of the compare match output frequency. It also simplifies the operation of counting external events.

## What happens when timer overflow occurs?

When it does overflow, it can generate an interrupt called the Timer Overflow Interrupt. Since the overflow occurs at periodic intervals, we can use the Timer Overflow Interrupt as a timer.

### How do I set a timer to interrupt AVR?

Steps to configure the Timer Interrupt:

1. Load the TCNT1 register with the value calculated above.
2. Set CS10 and CS12 bits to configure pre-scalar of 1024.
3. Enable timer1 overflow interrupt(TOIE1), the register is shown below.
4. Enable global interrupts by setting global interrupt enable bit in SREG.

What are the two types of AVR timer mode?

In AVR, timers are of two types: 8-bit and 16-bit timers.

How do you interrupt in AVR?

Steps to configure the Interrupts:

1. Set INT1 and INT0 bits in the General Interrupt Control Register (GICR)
2. Configure MCU Control Register (MCUCR) to select interrupt type.
3. Set Global Interrupt(I-bit) Enable bit in the AVR Status Register(SREG)
4. Handle the interrupt in the Interrupt Service Routine code.

## What do you use the timer for in ATmega?

Generally, we use timer/counter to generate time delays, waveforms or to count events. Also, the timer is used for PWM generation, capturing events etc. In AVR ATmega16 / ATmega32, there are three timers: Timer0: 8-bit timer. Timer1: 16-bit timer. Timer2: 8-bit timer.

### How does the interrupt model work in ATmega328?

Interrupt Model   When an interrupt event occurs:   Processor does an automatic procedure call   CALL automatically done to address for that interrupt   Push current PC, Jump to interrupt address   Each event has its own interrupt address   The global interrupt enable bit (in SREG) is automatically cleared

What is an external counter in ATMega32 used for?

External Counter: In this mode the unit is used to count events on a specific external pin on a MCU. Pulse width Modulation (PWM) Generator: PWM is used in speed control of motors and various other applications. Atmega32 has 3 timer units, timer 0, timer 1 and timer 2 respectively.

Can a timer be set to trigger an interrupt?

With that the timer over flow flag is set and it can be used to trigger an interrupt. Let us repeat the same example of blinking a LED connected to PD4 at 100ms delay with Timer 1 but this time using Interrupts. We have covered the Basics of AVR Interrupts, you may wish to go through it first.