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UART vs USART | Difference between UART and USART

This page compares UART vs USART and mentions difference between UART and USART. The page also provides links to difference between UART and SPI/I2C.

UART

• The full name is Universal Asynchronous Receiver/Transmitter.
• UART supports lower data rate.
• Receiver need to know baudrate of the transmitter before initiation of reception i.e. before communication to be established.
• UART is simple protocol, it uses start bit (before data word), stop bits (one or two, after data word), parity bit (even or odd) in its base format for data formatting. Parity bit helps in one bit error detection. This is shown in the figure-2.

UART vs USART, difference between UART and USART

➨UART Packet = 1 start bit(low level), 8 data bits including parity bit, 1 or 2 stop bit(high level)

• Data is transmitted byte by byte.
• UART generates clock internally and synchronizes it with data stream with the help of transition of start bit.
• It is also referred by RS232 .
• For long distance communication, 5V UART is converted to higher voltages viz. +12V for logic 0 and -12V for logic 1.

UART data mapping

USART

• The full name is Universal Synchronous/Asynchronous Receiver/Transmitter.
• As USART generates clocked data (i.e. synchronous clock generation), hence it supports higher data rate.
• Receiver need not be required to know the baudrate of the transmitter. This is derived from the clock signal and data line.
• The synchronous data is transmitted blockwise.
• USART can also generate data similar to UART. Hence USART can be used as UART but reverse is not possible.
• USART is complex and uses many different protocols (LIN, SPI, I2C, Modbus, IrDA etc.) to generate the data for transmissions.
• The figure-1 mentions how clock is used to detect and decode the data in the middle of the bit period.

Also refer RS232 interface and difference between UART vs SPI vs I2C>>.

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