In addition to defining electrical characteristics, RS232 specifies the signals used in serial cable pinouts and serial ports. Each pin in a 9 or 25 serial connector pinout has its own distinct function. These D-sub connectors can terminate with an RS232 female pinout or DB25 or DB9 male connector pins. RS232 manages communication flowing between the DTE and DCE using serial pinouts of either the DB9 or DB25 variety. Whether a DB9 serial pinout or a 25 pin connection is used, only three of the pins are required to connect terminal devices. RS232C retains the features of RS232 but uses 25 pins rather than a 9 pin serial pinout. The most recent version of the protocol is known as RS232C.

The RS232 protocol uses a 9 pin serial port that can have either male or female connectors.

A serial pinout diagram is presented below. The plugs contain sockets and pins, with each pin numbered and labeled.

Various manufacturers’ names may replace the DB in the specifications. They are commonly designated as DB-9 or DB-25 with the number used to differentiate between the pin counts. Serial communication devices make use of 9 or 25 pin D-type connectors for their cabled connections. The RS232 protocol specifies the operation mode, electrical standards, number of bits, and voltage levels to be used when transferring data between a DTE and DCE. For instance, a computer (DTE) might send the binary data “11011101” serially to the modem (DCE) which then replies by sending “11010101” back to the DTE device. Serial communication is implemented by the transmission of serial data between the DTE and DCE. The basic example of these two types of equipment defines a computer as a DTE device with a modem filling the role of DCE. DTE is the acronym for Data Terminal Equipment and DCE represents Data Communication Equipment. The formal specification of RS232 is that it is an interface which uses serial binary data exchange to communicate between DTE and DCE devices. The prefix RS denotes a Recommended Standard, and all of the EIA standards begin with those characters. What does RS232 stand for?ĭata transfer standards are developed by the Electronic Industry Association (EIA). Distances of up to 20 meters are the limit for reliable data transfer using the RS232 interface. It performs asynchronous transmission at a constant rate that is synchronized with the start pulse signal’s level. The RS232 protocol transmits data of wires employing signal levels that differ from the standard 5V in order to minimize signal interference. We will take a look at the serial port pinouts used to implement RS232 as well as some additional reference information concerning the protocol. The RS232 protocol is a popular serial interface that is used to connect computers to peripheral devices such as modems.

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