It is commonly found on older Arduino boards. AVR is binary option atm card family of microcontrollers developed since 1996 by Atmel, acquired by Microchip Technology in 2016.
AVR microcontrollers find many applications as embedded systems. They are especially common in hobbyist and educational embedded applications, popularized by their inclusion in many of the Arduino line of open hardware development boards. The original AVR MCU was developed at a local ASIC house in Trondheim, Norway, called Nordic VLSI at the time, now Nordic Semiconductor, where Bogen and Wollan were working as students. Atmel says that the name AVR is not an acronym and does not stand for anything in particular. The creators of the AVR give no definitive answer as to what the term “AVR” stands for.
However, it is commonly accepted that AVR stands for Alf and Vegard’s RISC processor. Among the first of the AVR line was the AT90S8515, which in a 40-pin DIP package has the same pinout as an 8051 microcontroller, including the external multiplexed address and data bus. The AVR 8-bit microcontroller architecture was introduced in 1997. By 2003, Atmel had shipped 500 million AVR flash microcontrollers.
The Arduino platform, developed for simple electronics projects, was released in 2005 and featured ATmega8 AVR microcontrollers. The AVR is a modified Harvard architecture machine, where program and data are stored in separate physical memory systems that appear in different address spaces, but having the ability to read data items from program memory using special instructions. 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. In 2006, Atmel released microcontrollers based on the 32-bit AVR32 architecture. This was a completely different architecture unrelated to the 8-bit AVR, intended to compete with the ARM-based processors.
Flash, EEPROM, and SRAM are all integrated onto a single chip, removing the need for external memory in most applications. Some devices have a parallel external bus option to allow adding additional data memory or memory-mapped devices. Program instructions are stored in non-volatile flash memory. Although the MCUs are 8-bit, each instruction takes one or two 16-bit words. AVR core must reside in the on-chip flash. Some small models also map the program ROM into the data address space, but larger models do not. The AVRs have 32 single-byte registers and are classified as 8-bit RISC devices.