General properties of AVR microcontrollers

Topics:

This applies to all types of AVR microcontrollers because they all use same AVR core technology. So lets go through some of them:

  • Ability to work at 1MIPS/MHz (MIPS – Millions Instructions Per Second);

  • On chip Flash memory (now tiny series have up to 8kB, mega up to 256kB) with write cycle not less than 1000 times;

  • On chip RAM memory (tiny series up to 512B, mega up to 8kB);

  • On chip EEPROM memory (tiny series up to 512B, mega up to 4kB) with write cycle not less than 100000 times;

  • Working frequencies up to 20MHz;

  • Protection fuses from unintentional reading and modification of program and data memories;

  • Ability to program in system – directly on board using ISP cable;

  • Four types of clock generators: Internal generator, RC generator of clock cycles, Internal generator with external crystal resonator, and External synchronisation;

  • Two or three power down modes;

  • Some microcontroller can work at very low voltages like 1.8V;

Other internal processor properties:

  • Static architecture where minimal frequency equal to zero;

  • ALU is connected directly to general purpose registers;

  • Most of commands are performed in one clock cycle;

  • Multilevel system of interrupts;

  • Many sources of interrupts – two of them are external;

  • Three level hardware stack.

I/O system properties:

  • Software configurable and selection of I/O ports;

  • Ports can be programmed as inputs and outputs independently to each other;

  • Input buffers uses Smith triggers on all pins;

  • Support of Internal Pull-Up resistors (about 35 to 120kOhm);

Peripheral devices vary from device to device. Refer to datasheets to find out what peripherals are included in concrete model. In general we can mention:

  • 8 bit timer counter with pre-scaler;

  • 16 bit timer counter with pre-scaler ;

  • Watch dog timer;

  • PWM generator;

  • Analog comparator;

  • ADC;

  • Hardware modulator;

  • SPI interface;

  • TWI (I2C) interface;

  • UART;

For additional information refer to datasheets.

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