The document provides an overview of AVR microcontrollers, including their history, architecture, types, and common peripherals. AVR microcontrollers were developed by Atmel beginning in 1996 and use on-chip flash memory for program storage. They are available in three categories - Tiny, Mega, and Xmega - with the Mega being the most popular. The AVR architecture employs 32 general purpose registers, static RAM, EEPROM, flash memory, timers/counters, and I/O ports. Common peripherals that can be interfaced include LEDs, 7-segment displays, switches, DC motors, and LCDs. Timers and interrupts are also discussed.

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2. Contents
• Introduction
• History of AVR
• AVR microcontroller
• Types of AVR microcontrollers
• AVR architecture
• GPIO Registers
• Interfacing
• Timers
• References
• Conclusion
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3. Introduction
• AVR stand for ADVANCED VIRTUAL RISC.
• AVR micro controllers is family of RISC microcontrollers from
Atmel.
• AVR was one of the first microcontroller families to use on-
chip flash memory for program storage.
• AVR microcontrollers are very popular, used in numerous
applications, particularly in project prototyping and also in
embedded devices.
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4. History of AVR
• AVR is a family of microcontrollers developed by Atmel beginning in
1996.
• The Atmel AVR has 8-bit RISC microcontrollers.
• The AVR architecture was conceived by two students at the
Norwegian Institute of Technology, Alf-Egil Bogen and Vegard Wollan.
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5. RISC microcontroller
• RISC stands for Reduced Introduction Set Computer.
• Till 1980 Trend was to build increasingly complex CPUs with complex
set of instructions like (CISC).
• Instruction execute in single cycle.
• RISC architecture CPUs capable of executing only a very limited
simple set of instructions.
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6. AVR microcontroller
• Devices range from 1 to 256KB.
• Pin count range from 8 to 100.
• Full code compatibility.
• Pin/feature compatible families.
• One set of development tools.
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7. Types of AVR microcontrollers
AVR microcontrollers are obtainable in three
categories:-
• Tiny AVR
• Mega AVR
• Xmega AVR
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8. TINY AVR
This microcontroller has Less
memory, small in size, only for
simpler applications.
• 0.5–16 KB program memory.
• 6–32-pin package.
• Small in size.
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9. MEGA AVR
• This microcontroller is the most popular having a good amount of
memory up to 256KB, higher no. of inbuilt peripherals and fit for
modest to difficult applications.
• 4–256 KB program memory
• 28–100-pin package
• Extended instruction set
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10. ATMEGA16 PIN DIAGRAM
• Atmega16 have total of 40 pins in which 32 are I/O
pins.
• VCC (PIN10) - Digital supply voltage.
• GND (PIN11) - Ground
• 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.
•
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11. CONTINUE…
• 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
• 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.
• XTAL 2 - Output to Inverting Oscillator Amplifier.
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12. XMEGA AVR
• This microcontroller is used commercially for compound
applications, which need large program memory and also
high speed.
• 16–384 KB program memory
• 44-100 pin
• Extended performance features such as DMA, Event
System.
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13. AVR ARCHITECTURE
• ALU
• 32 General Purpose Registers
• Static RAM
• EEPROM
• Flash
• Timer/Counter
• Comparator
• Watch Dog timer
• Protocols: UART, SPI, I2C
• I/O Ports
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14. Table 1: Basic registers of ATmega16
GPIO Registers
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15. INTERFACING OF LED
• A LED is an acronym for Light Emitting Diode and is basically an
electronic device which emits light when an electric current flows
through it.
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18. Numeric
Value
Dp G F E D C B A Address
0 0 0 1 1 1 1 1 1 0x3F
1 0 0 0 0 0 1 1 0 0x06
2 0 1 0 1 1 0 1 1 0x5B
3 0 1 0 0 1 1 1 1 0x4F
4 0 1 1 0 0 1 1 0 0x66
5 0 1 1 0 1 1 0 1 0x6D
6 0 1 1 1 1 1 0 1 0x7D
7 0 0 0 0 0 1 1 1 0x07
8 0 1 1 1 1 1 1 1 0x7F
9 0 1 1 0 1 1 1 1 0x6F18
Table 2: Truth Table of a CC 7-segment display

19. 7-SEGMENT DISPLAY INTERFACING
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• The seven segment display is the most common display device used
in many gadgets, and electronic appliances like digital meters, digital
clocks, microwave oven and electric stove, etc.
• Types of 7-Segment Displays:
Common Anode Display
Common Cathode Display

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22. INTERFACING OF SWITCH
• An electrical switch is any device used to interrupt the flow of
electrons in a circuit. Switches are essentially binary devices they are
either completely on (“closed”) or completely off (“open”).
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23. DC MOTOR INTERFACING
• An electric motor is an electrical machine that converts electrical
energy into mechanical energy.
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26. LCD INTERFACING
• LCD (Liquid Crystal Display) screen is
an electronic display module and find a
wide range of applications. A 16x2 LCD
display is very basic module and is very
commonly used in various devices and
circuits.
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29. TIMERS
• Timer is totally independent of the CPU.
• In AVR timers are of two types: 8-bit and 16-bit timers.
TIMER0 – 8-bit timer
TIMER1– 16-bit timer
TIMER2 – 8-bit timer
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30. INTERRUPTS
• Interrupts are basically events that require immediate attention by the
microcontroller.
• Atmega16 in total has twenty one (21) interrupts available.
• The available interrupts are categorized in two classes:
External Interrupts
Internal Interrupts
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31. Conclusion
• AVR is RISC architecture.
• AVR microcontrollers are very popular, used in numerous applications,
particularly in project prototyping and also in embedded devices.
• Programming is easy.
• AVR is Pipe lined processors resulting in faster execution.
• A watchdog to handle hanging software states is added.
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32. REFERENCES
• Mazidi Ali Muhammad, Mazidi Gillispie Janice, “The 8051
Microcontroller and Embedded System using Assembly and C”,
Pearson 2 𝑛𝑑 Edition.
• ATMega16 Datasheet.
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