USART is the acronym for Universal Synchronous-Asynchronous Receiver-Transmitter, and is the advancement of the old UART that was unable to handle synchronous communications; in computers, it deals with the management of communication via the RS-232 interface.
Generally, in the communication between devices, there is a transmitter and receiver that can exchange data bidirectionally, thus it happens for example in the communication between the microcontroller and third-party peripherals.
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