RS232 Serial Port Connector Pin Layout

RS-232 is a serial communications standard that provides asynchronous and synchronous communication capabilities, such as hardware flow control, software flow control, and parity check. It has been widely used for decades. Almost all gears, instruments with digital control interface, and communications devices are equipped with the RS-232 interface. The typical transmission speed of an RS-232 connection is 9600 bps over a maximum distance of 15 meters.

The following document describes the functions of the pins on the RS232 9 and 25 pin Sub-D connectors 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 Equipment ) or Modem Side.

Using the ActiveXperts Serial Port Component you can send and receive data and control the RS232 port.

RS232 9 Pin connector (DB-9)

1	DCD	Data Carrier Detect
2	RD	Received Data
3	TD	Transmitted Data
4	DTR	Data Terminal Ready
5	GND	Signal Ground
6	DSR	Data Set Ready
7	RTS	Request To Send
8	CTS	Clear To Send
9	RI	Ring Indicator

RS232 25 Pin connector (DB-25)

1	PG	Protective Ground
2	TD	Transmitted Data
3	RD	Received Data
4	RTS	Request To Send
5	CTS	Clear To Send
6	DSR	Data Set Ready
7	SG	Signal Ground
8	CD	Carrier Detect
9	-	Reserved
10	-	Reserved
11	-	Unassigned
12	SCD	Secondary Carrier Detect
13	SCTS	Secondary Clear To Send
14	STD	Secondary Transmit Data
15	TC	Transmitter Clock
16	SRD	Secondary Received Data
17	RC	Receiver Clock
18	-	Unassigned
19	SRTS	Secondary Request To Send
20	DTR	Data Terminal Ready
21	SO	Signal Quality Detector
22	RI	Ring Indicator
23	DRS	Data Rate Selector
24	DRS	Data Rate Selector
25	-	Unassigned