RS485 Serial Port Connector Pin Layout

RS-485 is a serial communications standard that provides asynchronous communication capabilities, such as hardware flow control, software flow control, and parity check. It has been widely used for decades.

Because RS-485 signals are transmitted over twisted-pair cabling, the connections are less sensitive for noise. It can span relatively large distances (up to 4000 feet).

The following document describes the functions of the pins on the RS-485 9 pin Sub-D connector used in serial communications. The pins in the images are as viewed from the pin side (not the solder or printed circuit board side). The male sockets are used on the DTE (Data Terminal Equipment ) or PC side. The female sockets are on the DCE (Data Communication Equipmnet ) or Modem Side.

Using the ActiveXperts Serial Port Component you can send and receive data and control the RS485 port.

RS485 9 Pin connector (DB-9)

1	GND	Common Ground
2	CTS+	Clear To Send +
3	RTS+	Ready To Send +
4	RXD+	Received Data +
5	RXD-	Received Data -
6	CTS-	Clear To Send -
7	RTS-	Request To Send -
8	TXD+	Transmitted Data +
9	TXD-	Transmitted Data -