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What is the Minimum System on the Microcontroller?

avr minimal circuit

avr minimal circuit

The minimum system circuit of a microcontroller is a series of minimal so the microcontroller can work.

ATmegga AVR chip is equipped with an internal oscillator and thus no need external crystal for CPU clock source in order to save costs.

AVR microcontroller minimum system is very simple, just connect the VCC and AVCC to the DC +5V power supply voltage. Then GND and AGND with the ground. No need an additional crystal and reset pin is not connected to anything. With this circuit, AVR microcontroller has been able to work normally, but you can not reset the microcontroller manually. If you want to activate the reset pin with a button to trigger it, then connect the reset pin on your microcontroller with pull circuit made up of a 10k resistor and capacitor 10uF.

This circuit works for all AVR microcontroller family as ATMega8535, ATMega8, ATmega32, ATmega16 and others.

If you want to use larger crystals from 8MHz to your microcontroller circuit, then you can use an external crystal. You can see a more complete circuit on this page or this one.

AVR ATMega8 Schematic Circuit with Eagle Software



ATMega8 Schematic Circuit (Minimum system) is a support circuit for the microcontroller.

Without this support circuit, the microcontroller will not be able to work.

Minimum system for microcontrollers consist of several components. The components are : crystal, capacitors, and the reset circuit (consisting of resistors and capacitors).

And the crystal must be combined by two capacitors. The capacity of this capacitor should be in accordance with the AVR ATMega8 datasheet.

RESET pin on AVR ATMega8 must be pull up with a 4K7 ohm resistor and stabilized with ‘100nF capacitors’.

You have to make the pin as a downloader port. pin of the downloader port must meet a standard sequence. The pin sequence is: MOSI, MISO, SCK, RESET, GROUND.

This AVR ATMega8 schematic is made with the EAGLE software.

ATMega16 Schematic Circuit Tutorial



Many projects can be built from a microcontroller such as control and monitoring project. AVR ATmega16 can work when there are several supporting components such as resistors and capacitors in the circuit. ‘Reset’ feature on ATmega16 microcontroller must pull up using resistors (Also applies to the other AVR ATMega microcontroller). The series of pull up on the reset button typically use 4.7 Kohm resistor and stabilized with 100nF capacitor.

For AVR ATmega16 You can use up to 16 MHz crystal. But if you use the AVR ATMega16L you can only use 0-8MHz. Crystal components is enclosed by two capacitors whose capacity is set in microcontroller datasheet. However, it is usually used 22pF.

The downloader pin must be arranged  like the downloader standart pin (MOSI, MISO, SCK, RESET, GROUND).

Once you complete all the components of the minimum system, the microcontroller you’ve been able to work properly.