![]() The resistor and capacitor values may differ from the diagram’s values and depend on the required reset pulse duration. An external circuit may be required if there are special requirements for the reset pulse duration (in case of a slow rise of the supply voltage). Nowadays, every modern microcontroller probably has a Power-on-Reset circuit. This is how the initial reset of the microcontroller was done. The bundling for previous microcontroller models necessarily included an initial reset circuit consisting of a resistor and a capacitor, which ensured that the reset input is rising gradually when the power was turned on. But, if the user program does not use interrupts, it can be located directly at address zero. Usually, this is a jump to the program start address. All I/O registers take their initial values during reset, and the command located in the reset vector (at address zero) is executed. The Reset pin is used to generate a reset signal on the microcontroller. However, this recommendation is not implemented even in the Arduino boards, and the AVCC pin is simply connected to VCC. The datasheet is recommended to connect AVCC to VCC with a 10µH inductance and GND with 0.1♟ capacitance. If you plan to use the ADC, a filter should be added to the power supply circuit to reduce noise. Even if you are not going to use the ADC, you have to power it: connect VCC to AVCC and digital ground to analog. The ATmega328P has a dual power supply: VCC and GND (pins 7 and 8) are used to power the digital circuits of the microcontroller AVCC and GND (pins 20 and 22) are used to power the analog to digital converter. It should be placed as close as possible to the microcontroller’s supply pins to minimize the parasitic inductance and the resistance of the supply wires. It is recommended to install a 0.1MF ceramic capacitor between VCC and GND to suppress high-frequency interferences. For the ATmega328P, the upper limit of the recommended supply voltage is 5,5V, the absolute maximum is 6V. ![]() The power supply voltage is connected to the pins VCC and GND of the microcontroller and must not exceed the datasheet’s value. When it comes to a single microcontroller, you always need to have its pinout at hand. When we work with Arduino boards, we don’t think about the correspondence of the microcontroller’s physical pins used in the Arduino IDE. ![]() Before we start to look at the pinout of the ATmega328P, I think it is necessary to describe the pinout of the ATmega328P. ![]()
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