This document discusses the Universal Asynchronous Receiver/Transmitter (UART) communication protocol. It explains that UART is an asynchronous serial communication protocol commonly used for communication between microcontrollers and peripheral devices. It operates by framing data bits with start and stop bits across two or more wires. The document covers UART fundamentals like frame formatting, transmission and reception of data, baud rate calculation, and differences between UART and Universal Synchronous/Asynchronous Receiver/Transmitter (USART). It also provides block diagrams of the UART module and examples of configuring baud rates on microcontrollers.