Both, Parallel and Serial modes of communication have certain advantages and disadvantages over one another. The serial communication is a preferred option due [[wysiwyg_imageupload::]]to its ability of long distance communication with error detection capability. The microcontrollers consist of an inbuilt hardware unit known as USART (Universal Synchronous Asynchronous Reception and Transmission) to facilitate serial transfer of data. Before starting USART, some general terms related to communication need to be understood. These terms are explained below.Asynchronous Communication: In this type of communication, both Transmitter (Tx) and Receiver (Rx) work on different clocks which means that they are not synchronized. Start and Stop bits are also sent with each Data byte to identify the data. Synchronous Communication: In this type of communication, both Tx and Rx are synchronized with the same clock and no Start or Stop bits are used.Full-duplex Communication: When either of the devices can send and receive data at the same instant, they are said to have full-duplex communication.