Introduction Of AVR Microcontroller

type ofAVR microcintroller chips

 Introduction to AVR Microcontroller & Short History 

AVR stand for Alf Vegard RISC is a modified Harvard architecture, 8-bit RISC, single chip microcontroller which was designed by two student of Norwegian Institutte of Technology, Alf-Egil Bogen and Vegard wollan and then was developed by Atmel in 1996.. The AVR was one of the first microcontroller families to use on-chip flash memory for program storage, as opposed to OTP ROM, EPROM or EEPROM used by other microcontrollers at that time.

                         ATmega & Xmega AVR chips became extremely popular after they were designed into the 8-bit Arduino platform. 

Family of AVR Microcontroller


AVRs Microcontroller are generally classified into following:

  • tinyAVR — the ATtiny series
    • 0.5–16 kB program memory
    • 6–32-pin package
    • Limited peripheral set
  • megaAVR — the ATmega series
    • 4–512 kB program memory
    • 28–100-pin package
    • Extended instruction set (multiply instructions and instructions for handling larger program memories)
    • Extensive peripheral set
  • XMEGA — the ATxmega series
    • 16–384 kB program memory
    • 44–64–100-pin package (A4, A3, A1)
    • Extended performance features, such as DMA, “Event System”, and cryptography support.
    • Extensive peripheral set with ADCs
  • Application-specific AVR
    • megaAVRs with special features not found on the other members of the AVR family, such as LCD controller, USB controller, advanced PWM, CAN, etc.


Features of ATmega32 Microcontroller

  • 32K bytes of In-System Programmable Flash Program memory with Read-While-Write capabilities
  • 1024 bytes EEPROM
  • 2K byte SRAM
  • 32 general purpose I/O lines
  • JTAG interface for Boundary scan
  • On-chip Debugging support and programming
  • 3 flexible Timer/Counters with compare modes
  • Internal and External Interrupts
  • Serial programmable USART
  • Byte oriented Two-wire Serial Interface ( I2C )
  • 8-channel, 10-bit ADC
  • Programmable Watchdog Timer with Internal Oscillator
  • SPI serial port
  • 6 software selectable power saving modes

Pinout Description of AVR Microcontroller

Pinout of AVR Microcontroller


Port A (PA7..PA0) :-   Port A   serves  as the  analog  inputs  to the  A/D Converter.   Port A  also serves as  an  8-bit  bi-directional I/O port, if the A/D Converter is not used. Port pins. Port pins  metrical   drive characteristics with  both  high sink and  source capability. When  pins PA0 to PA7 are used as inputs and are  externally  pulled low, they will source current if the internal pull-up.

Port B (PB7..PB0) :-      Port B   is an   8-bit bi-directional  I/O port with internal pull-up  resistors  (selected for each bit).

Port C (PC7..PC0) :-      Port C   is an  8-bit bi-directional  I/O port with internal pull-up resistors  (selected for each bit).

Port D (PD7..PD0) :-     Port D  is an  8-bit bi-directional I/O port  with internal pull-up  resistors  (selected  for each  bit). 

RESET :-     Reset Input.  A low level on this pin for longer than the minimum pulse length will  generate  a reset, even if the  clock is not  running.   The minimum  pulse  length is given in  Shorter pulses  are not guaranteed to generate a reset.

XTAL1 :-    Input to the  inverting  Oscillator amplifier and input to the internal clock operating circuit.

XTAL2 :-    Output from the  inverting  Oscillator  amplifier.

AVcc : –     AVcc  is the supply voltage pin for Port A and the A/D Converter.

AREF  :-      AREF  is  the  analog  reference  pin  for  the   A/D Converter.