To ensure that communications are possible between a variety of RS232 devices it is necessary that standard RS232 pin outs are used. Although a variety of connectors are used, the pin outs for each type of connector has to be standardized so that it is possible to know how to connect to them, and to be able to use standard RS232 cables.
The most common connectors use the D-type often also called a sub-D connector and both 9 way and 25 way versions are used. In addition to this other types of connector may be used on occasions.
When using RS232, two main types of equipment are nominated. One is a data Terminal Equipment, DCE and the other is known as the Data Terminal Equipment, DTE. These abbreviations are widely used within RS232 and other communications terminology.
By using the pin outs as detailed below the RS232 cables used should be a “one to one” configuration. This considerably simplifies the manufacture of RS232 cables and often means that standard cables can be used.
RS-232 25 Pin Connections and Functions
The RS232 (EIA-232-A) specification provides a full set of details for a wide variety of connections that can be used with RS232. While many of them are not normally known, they may be used in some circumstances and therefore the details are provided here for reference.
RS232 25 pin signal definition for the DTE device – looking into the DTE connector
DTE device is often a PC.
RS232 25 pin signal definition for the DCE device – looking into the DCE connector
DTE device is often a device such as a modem.
By using these configurations it means that an RS232 cable connecting a DTE to a DCE will be wired in a one-to-one configuration, i.e. pin 1 to pin 1, etc.
RS-232 9 Pin Connections, Functions and Pin-outs
Although the RS232 25 pin configuration with a 25 way D-type connector is very widely used, in many applications the smaller 9 way D-type connector is used in many applications. It provides an obvious size and cost benefit. Also the RS232 9pin configuration is quite sufficient in most circumstances because many of the lines available for RS232 signalling are rarely used. This means that the 9 way connector is able to provide all the required connectivity for most applications.
RS232 9pin signal definition for the DTE device – looking into the DTE connector
DTE RS232 device is often a PC.
RS232 9pin signal definition for the DCE device – looking into the DCE connector
DCE device is often a modem.
By using these configurations it means that an RS232 cable connecting two RS232 devices, i.e. a DTE to a DCE will be wired in a one-to-one configuration, i.e. pin 1 to pin 1, etc.
RS232 is still widely used throughout the electronics and telecommunications industries. When using this form of serial communications system it is essential to ensure that the correct connections are being used. Accordingly it is necessary to check the RS232 pin outs when making any leads or other connections. Both RS232 25 pin and RS232 9pin connectors are used when making connections, so checking the correct connector and pin connections is important to ensure that communications can take place.