Arduino A000066, Product Reference Manual, Page: 6 / 13

Arduino® UNO R3
6 / 13 Arduino® UNO R3 / Rev. 01 - 25/11/2021
3.2 Processor
The Main Processor is a ATmega328P running at up tp 20 MHz. Most of its pins are connected to the external
headers, however some are reserved for internal communication with the USB Bridge coprocessor.
3.3 Power Tree
Power tree