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General Information - 

Universal Asynchronous Receiver Transmitter (UART)

A UART is a chip that is used for building serial communication devices such as modems and serial ports. The chips has a transmitter section and a receiver section. The transmitter converts the (8-bit) bytes into a serial stream of data bits as they are prepared for transmission. The received takes the incoming stream of bits and groups them into 8-bit chunks so they can be reconstructed as bytes.

The UART also monitors input control lines and has the ability to change the state of output lines on the chip depending on the program code running at the time.

UARTs can be wired as either Data Terminal Equipment (DTE ) or Data Communication Equipment (DCE). They are controlled by a clock usually running at 1.84MHz and have a maximum throughput of 115Kbps. Special high speed serial ports are available with higher speed clocks such as 7.37MHz and 14.7MHz. A buffer is also used to temporarily hold incoming data. This buffer varies by the model and is usually very small.

Type of Uart's

• 16C450
• 16450
• 16550 uses a 16 byte buffer
• 16550af
• 16750 uses a 64 byte transmit buffer and a 56 byte receive buffer

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