RS-232 Serial Port

When wiring your connections to the 9-pin or 25-pin port connector, it's easy to become confused with the pin numbers. Looking at the pictorial below, it should become clear where each pin is located.
If you look at the port on the rear of you PC, you'll notice there is always a 'male'-type connector. Counting from the top row, the pins start at number '1' through to '5'. The bottom rows start at pin '6' and end at pin '9'. Just remember that the 'female'-type connector has the pin designations inverted. The same rules apply to the 25-pin connector.

Front/Rear views of the 9-pin RS-232 Serial port

This table should help you ascertain the serial port's connections...

9-pinDesignation25-pin
1 DCD - Data Carrier Detect 8
2 RXD - Receive Data 3
3 TXD - Transmit Data 2
4 DTR - Data Terminal Ready 20
5 GND - Ground Connection 7
6 DSR - Data Set Ready 6
7 RTS - Request To Send 4
8 CTS - Clear To Send 5
9 RI - Ring Indicator 22

Scrolling line

Best Regards... Pete

http://www.keirle.fsnet.co.uk