External Interfaces

The Serial Port Interface Standard

The serial port interface for connecting two devices is specified by the TIA/EIA-232C standard published by the Telecommunications Industry Association.

The original serial port interface standard was given by RS-232, which stands for Recommended Standard number 232. The term "RS-232" is still in popular use, and is used in this guide when referring to a serial communication port that follows the TIA/EIA-232 standard. RS-232 defines these serial port characteristics:

• The maximum bit transfer rate and cable length
• The names, electrical characteristics, and functions of signals
• The mechanical connections and pin assignments

Primary communication is accomplished using three pins: the Transmit Data pin, the Receive Data pin, and the Ground pin. Other pins are available for data flow control, but are not required.

Other standards such as RS-485 define additional functionality such as higher bit transfer rates, longer cable lengths, and connections to as many as 256 devices.

What Is Serial Communication?

Connecting Two Devices with a Serial Cable

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