The RS-232 standard interface (also known as EIA RS-232) is one of the commonly used serial communication interface standards. It was jointly established in 1970 by the Electronic Industries Association (EIA) in conjunction with Bell Systems, modem manufacturers and computer terminal manufacturers. Established, its full name is “Technical Standard for Serial Binary Data Exchange interface Between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)”.
In serial communication, both parties are required to use a standard interface so that different devices can be easily connected for communication. The RS-232-C interface (also known as EIARS-232-C) is currently the most commonly used serial communication interface. (The “-C” in “RS-232-C” only indicates the version of RS-232, so it is the same as the abbreviation of “RS-232”).
It is a standard for serial communication formulated by the Electronic Industries Association (EIA) of the United States in conjunction with Bell Systems, modem manufacturers and computer terminal manufacturers in 1970. Its full name is “Technical Standard for Serial Binary Data Exchange Interface Between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)”. The standard stipulates that a 25-pin DB-25 connector is used for each connector. The signal content of each pin is specified, and the levels of various signals are also specified. Later, IBM’s PC simplified rs232 into a DB-9 connector, which became the de facto standard. The RS-232 port of industrial control generally only uses three lines of RXD, TXD, and GND.
Less signal lines
The RS-232 bus specifies 25 lines, including two signal channels, namely the first channel (called the main channel) and the second channel (called the secondary channel). The RS-232 bus can be used to achieve full-duplex communication, usually the main channel is used, and the secondary channel is used less. In general applications, full-duplex communication can be realized by using 3 to 9 signal lines, and a simple full-duplex communication process can be realized by using three signal lines (receiving line, sending line and signal ground).