What is AVR Microcontroller：Features, Architecture and Application 2022

AVR microcontroller is a relatively new microcontroller introduced by Atmel, whose distinctive features are high performance, high speed and low power consumption. AVR microcontroller instructions are word-based, and most of them are single-cycle instructions.

What is AVR Microcontroller

In 1997, Mr. A and Mr. V of ATMEL's developed a high-speed 8-bit microcontroller with RISC streamlined instruction set using ATMEL's new Flash technology.

1. Features of AVR Microcontroller

Compared with other 8-Bit MCUs, the best features of AVR 8-Bit MCUs are

1. Harvard architecture with 1 MIPS / MHz high-speed operational processing capability.
2. Super Functional Streamlined Instruction Set (RISC) with 32 general-purpose working registers, overcoming the bottleneck caused by a single ACC for processing, as in the 8051 MCU.
3. fast access register set, single cycle instruction system, greatly optimized target code size, execution efficiency, some models with very large FLASH, especially suitable for development using high-level languages.
4. Same as HI/LOW of PIC when used as output, can output 40mA (single output), can be set as tri-state high impedance input or pull-up resistor input when used as input, with the capability of 10mA - 20mA potting current.
5. On-chip integration of multiple frequency RC oscillators, automatic power-on reset, watchdog, start-up delay and other functions, simpler peripheral circuits, more stable and reliable systems.
6. Most AVRs are rich in on-chip resources: with E2PROM, PWM, RTC, SPI, UART, TWI, ISP, AD, Analog Comparator, WDT, etc..
7. Most AVRs have IAP function in addition to ISP function, which is convenient for upgrading or destroying applications.

2. AVR Microcontroller Architecture

1. Internal structure

In terms of internal architecture, the AVR ATmega microcontroller consists of an AVR CPU, various inputs/outputs, timing, analog-to-digital conversion, counters/timers, serial functions and various other component functions, which Atmel refers to as "peripheral functions". Apart from the I/O functions, the main difference between AVR microcontrollers is the amount of flash memory and I/O functions on board. All 8-bit parts are basically using the same AVR CPU core.

RISC architecture

• 131 instructions
• 32 8-bit general purpose registers
• Maximum clock frequency of 20 MHz (20 MIPS operations)

On-board memory

• Fast program memory (up to 256kB)
• On-board EEROM (up to 4kB)
• Internal SRAM (Static Random-Access Memory) (up to 32kB)

Operating Voltage

• VCC = 1.8V ~ 1.5V DC

2. Internal memory

All AVR devices contain different amounts of memory, which can be broadly classified into 3 types.

• Flash memory (flash): stores program code
• SRAM (static random access memory): stores temporary data (e.g. program variables, stack)
• EEPROM: stores data that needs to be retained continuously during software changes and switching on/off

Flash memory and EEPROM can load data from external sources and retain the data in them when the AVR is powered off. SRAM, on the other hand, is volatile and the contents saved in it are lost when the AVR loses power.

AVR Microcontroller Applications and Advantageous Features

Microcontrollers have been widely used in military, industrial, home appliances, smart toys, portable smart meters and robot making, making the product function, precision and quality substantially improved with simple circuit, low failure rate, high reliability and low cost. There are many kinds of microcontrollers, in the simple robot production and innovation, why choose AVR microcontroller?

1. Easy to learn, low cost

First of all, for non-professionals, the main reason for choosing AVR microcontroller is that the threshold for entering AVR microcontroller development is very low, as long as you can operate a computer you can learn AVR microcontroller development. AVR microcontroller beginners only need an ISP download line, edit, debug through the software program directly online into the AVR microcontroller, that is, you can develop the AVR microcontroller series of various packages of devices. AVR microcontroller is therefore known in the industry as "a line to play the world.

Secondly, AVR microcontroller is easy to upgrade. AVR program writing is directly on the board to modify the program, burning and other operations, so it is easy to upgrade the product.

Again, AVR microcontroller is inexpensive. Learning AVR microcontroller can use ISP online download programming method (i.e. write the compiled program on PC to the program memory of microcontroller), no need to buy emulator, programmer, eraser and chip adapter, etc., can carry out all AVR microcontroller development applications, which can save a lot of development costs. The program memory can be erased and written more than 10,000 times without producing scrap.

2. High speed, low power consumption, confidentiality

As we know that the AVR microcontroller is a high-speed embedded MCU

a. AVR microcontroller has pre-fetch instruction function, that is, when executing an instruction, pre-fetch the next instruction in, so that the instruction can be executed in a clock cycle.

b. Multi-accumulator type, fast data processing speed. AVR microcontroller has 32 general-purpose working registers, which is equivalent to having 32 overpasses for fast passage.

c. interrupt response speed. AVR microcontroller has multiple fixed interrupt vector entry address, which can respond to interrupt quickly.

d. AVR microcontroller consumes low energy. For typical power consumption case, WDT is 100nA when off, which is more suitable for battery-powered application devices. Some devices can operate at as low as 1.8V.

e. The AVR microcontroller has good secrecy performance. It has unbreakable bit encryption lock LOCkBit technology, the secrecy bit unit is hidden deep inside the chip and cannot be seen by electron microscope.

3. Strong I/O port function, with A/D conversion and other circuits

1. The I/O port of AVR microcontroller is a real I/O port, which can correctly reflect the real situation of I/O port input/output. Industrial-grade products, with high current (filling current) 10 ~ 40mA, can directly drive silicon SSR or relay, saving peripheral driver parts.

2. AVR microcontroller with analog comparator, I/O port can be used as A/D converter, can be composed of inexpensive A/D converter. ATmega48/8/16 and other devices have 8-way 10-bit A/D.

3. Some AVR microcontrollers can form zero peripheral components microcontroller system, so that this type of microcontroller can work without additional components, simple and convenient, and low cost.

4. AVR microcontroller can reset the start reset, in order to improve the reliability of the microcontroller work. There is a watchdog timer to implement security protection, to prevent the program from going haywire (fly), improve the product's anti-interference ability.

4. There is a powerful timer / counter and communication interface

Timer / counter T / C has 8-bit and 16-bit, can be used as a comparator. Counter external interrupt and PWM (also can be used as D / A) for control output, some models of AVR microcontroller has 3 to 4 PWM, is the ideal device for motor stepless speed control.

AVR microcontroller has serial asynchronous communication UART interface, does not occupy the timer and SPI synchronous transmission function, because it has high-speed characteristics, so it can work in general standard integer frequency, and baud rate up to 576K.

There is also IAP function, which is convenient for upgrading or destroying applications.

5. AVR microcontroller from the market point of view

-Price ratio: Most of the AVR models have a high price/performance ratio, and the models with outstanding price/performance ratio are: atmega48, atmega8, atmega16, atmega169P

-Supply: For general-purpose models, the supply of AVR microcontroller is stable

-Market share: At present, the market share of AVR is still not as good as PIC and 51, but, the advantages of AVR make the market share of AVR has been expanding, and the annual usage of AVR has been rising.