Editing Universal asynchronous receiver-transmitter (section)

===Application===
Transmitting and receiving UARTs must be set for the same bit speed (Baud rate), character length, parity, and number of stop bits for proper operation. The receiving UART may detect some mismatched settings and set a "framing error" flag bit for the host system; in exceptional cases, the receiving UART will produce an erratic stream of mutilated characters and transfer them to the host system.

Typical serial ports used with personal computers connected to modems use one start bit, eight data bits, no parity, and one stop bit; for this configuration, the number of ASCII characters per second equals the bit rate divided by 10.

Some very low-cost [[home computers]] or [[embedded systems]] that lack a physical UART may instead [[Emulator|emulate]] the protocol with software by sampling the state of an input port or directly manipulating an output port for data transmission. While very CPU-intensive (since the CPU timing is critical), the UART chip can thus be omitted, saving money and space. The technique is known as [[bit-banging]].