Almost done with the documentation about ATmega328P.
Thank you for links.
I have another question, I am planning to use USB in order to send/receive data from PC/Smartphone. I have found also that Arduino UNO includes the USB Serial Light Adapter.
Which can be used for the purpose of sending/receiving data from PC via USB connection. But I couldn't find this information in the document above.
Do you know what documentation should I read in order to be able to use the USB Serial Light Adapter (also low level if possible)?