What is USART? What are the advantages of USART?

Subject Peripheral and Interfacing
NU Year Set: 5.(a) Marks: 1+3=4 Year: 2017

A USART (Universal Synchronous/Asynchronous Receiver/Transmitter) is a microchip that facilitates communication through a computer's protocol port using the RS-232C protocol. 

A USART -- a Universal Synchronous/Asynchronous Receiver/Transmitter -- is a microcontroller peripheral that converts incoming and outgoing bytes of data into a serial bit stream. Hmm. The definition of a USART is identical to that of a UART, but with "synchronous" added to the term. Surely there are some more meaningful differences? Otherwise, a USART would just be known as a UART.
A USART, on the other hand, can be set up to run in synchronous mode. In this mode the sending peripheral will generate a clock that the receiving peripheral can recover from the data stream without knowing the baud rate ahead of time. Alternatively, the link will use a completely separate line to carry the clock signal. The use of the external clock allows the data rate of the USART to be much higher than that of a standard UART, reaching up to rates of 4 Mbps.
USART and UART peripherals have definitely different capabilities and can be useful in different situations, so a developer may find both peripherals onboard a standard microcontroller. For example, take a microcontroller that is targeting low-power design such as the STM32 family. The STM32 parts have both a USART and a UART peripheral on-chip. The USART is meant to do all of the "heavy lifting" serial communication during periods of “high” energy consumption. When the microcontroller is asleep and in a low power mode, though, the UART peripheral can handle low-speed communications while offering a reduced energy footprint.

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