RS-232

RS-232 is a Recommended Standard (RS) describing the most widely used type of serial communication. The RS-232 protocol is used for asynchronous data transfer as well as synchronous transfers using HDLC, Frame Relay, and X.25. RS-232 is also known as EIA-232.

The RS-232 line protocol is very popular for low-speed data signals. RS-232 signals are carried as single voltages referred to a common ground signal. The voltage output level of these signals varies between –12V and +12V. Within this range, voltages between –3V and +3V are considered inoperative and are used to absorb line noise. Control signals are considered operative when the voltage ranges from +3 to +25V.

The RS-232 line protocol is an unbalanced protocol, because it uses only one wire, and is susceptible to signal degradation. Degradation can be extremely disruptive, particularly when a difference in ground potential exists between the transmitting and receiving ends of a link.

The RS-232 interface is implemented in a 25-pin D-shell connector and supports line rates up to 200 Kbps over lines shorter than 98 feet (30 meters).

Note: RS-232 serial interfaces cannot function error-free with a clock rate greater than 200 KHz.