RS232

 RS232 Pinout:
The RS232 specification only defines the pin-out for a 25 pin D-sub connector;
however, the 9 pin is used more often (defined by EIA-574).
A 26 pin connector is also called out in the RS232 spec.
EIA-561 calls out an 8 pin connector (RJ-45).
RS232C indicates a DB25, RS232D indicates an RJ45.
Although this site, in general, calls out DB9 and DB25 style connectors, the real term for a 9-pin D-sub is DE9.
A listing of Dsub connector manufacturers is listed on the D-Sub Connector Manufacturers page.
D-Sub Shell Dimensions,
D-Sub Insert Arrangments.
Many RS232 pinouts listed here are also listed on the RS232 Pinout page.
An RS232 Pinout may also be termed RS232 Signal Assignments.

RS232 DB-9 Connector Pin Out

Pin #	Signal Name	Signal Description
1	CD	Carrier Detect
2	RXD	Receive Data
3	TXD	Transmit Data
4	DTR	Data Terminal Ready
5	GND	Signal Ground / Common
6	DSR	Data Set Ready
7	RTS	Request To Send
8	CTS	Clear To Send
9	RI	Ring Indicator

RS232 Pinout, DB-25 Connector Signal Assignments

Pin #	Signal Name	Signal Function	Pin #	Signal Name	Signal Function
1	----	Protective Ground	14	SBA	2nd Transmitted Data
2	TXD	Transmitted Data	15	DB	DCE Element Timing
3	RXD	Receive Data	16	SBB	2nd Received Data
4	RTS	Request To Send	17	DD	Received Element Timing
5	CTS	Clear To Send	18	-----	Unassigned
6	DSR	Data Set Ready	19	SCA	2nd Request To Send
7	GND	Signal Ground/Common	20	DTR	Data Terminal Ready
8	CD	Carrier Detect	21	CG	Signal Quality Detector
9	---	+Voltage	22	RI	Ring Detector
10	---	-Voltage	23	CH/CI	Data Signal Rate Detector
11	---	----	24	DA	DTE Element Timing
12	SCF	2nd Line Detector	25	----	Unassigned
13	SCB	2nd Clear To Send	--	---	---

 

RS232 RJ-45 Connector Pin Out

Pin #	Signal Name	Signal Description
1	RI	Ring Indicator
2	DCD	Carrier Detect
3	DTR	Data Terminal Ready
4	GND	Signal Ground / Common
5	RXD	Receive Data
6	TXD	Transmit Data
7	CTS	Clear To Send
8	RTS	Request To Send

TXD: Transmit Data; The data sent from the Data Terminal and received by the
Data Set. [RS232 Transmit]

RXD: Receive Data; The data sent from the Data Set and received by the Data
Terminal. [RS232 Receive]

DTR: Data Terminal Ready; Used by the Data Terminal to signal to the Data Set
that it is ready for operation, active high.

DSR: Data Set Ready; Used by the Data Set to signal to the Data Terminal that
it is ready for operation and ready to receive data, active high.

RTS: Request To Send; Used by the Data Terminal to signal the Data Set that it
may begin sending data. The Data Set will not send out data with out this signal, active high.

CTS: Clear To Send; Used by the Data Set to signal the Data Terminal that it may
begin sending data. The Data Terminal will not send out data with out this signal, active high.

CD: Carrier Detect; Used by the Data Set to indicate to the Data Terminal that
the Data set has detected a carrier (of another device).

RI: Ring Indicator; Used by the Data Set to indicate to the Data Terminal that a
ringing condition has been detected.

GND: Ground; The common return for all signals on the interface. [RS232 Ground]

When using Software Flow Control(XON, XOFF); you only need 3 lines, TX (data),
RX (data), and GND. XON being equal to ready, XOFF equal to not ready.