Universal asynchronous receive transmit (UART)
UARTs are used for serial communication between systems; they can be either
half duplex (send or receive) or full duplex (send and receive at the same time).
Also known as an RS232 connection the microcontroller UART can provide
the connection with a PC or another microcontroller-based system. Figure 4.25
illustrates possible connection arrangements. In a minimum connection there
could be only two transmission lines, transmit (Tx) and receive (Rx) as shown
in Figure 4.26. The data is conveyed as a bit stream, either transmit or receive,
and the speed is defined by the baud rate i.e. the bits per second.