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 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.
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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