RS232 Connectors / Pinout

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The most common connectors for RS232 communication are

 

9-pole SUB D9 (EIA/TIA 574 standard). Introduced by IBM and widely used. See below.
25-pole SUB D25 (RS232-C). This is the original connector introduced for the RS232 standard. It provides a secondary communication channel.
8-pole RJ45 (RS232-D, according to EIA/TIA-561 standard).

 

 

 

RS232 SUB D9 Pinout

 

View: Looking into the male connector.

Pinout: From a DTE perspective (the DTE transmits data on the TX Transmit Data line, while the DCE receives data on this line)

 

PT_connector_rs232subd9

 

Pin No.

Signal Name

Description

DTE in/out

1

DCD

Data Carrier Detect

Input

2

RX

Receive Data

Input

3

TX

Transmit Data

Output

4

DTR

Data Terminal Ready

Output

5

SGND

Signal Ground

-

6

DSR

Data Set Ready

Input

7

RTS

Request To Send

Output

8

CTS

Clear To Send

Input

9

RI

Ring Indicator

Input

 

 

 

RS232 SUB D25 Pinout

 

View: DTE perspective, looking into the male connector

 

PT_connector_rs232subd25

 

Pin No.

Signal Name

Description

1

-

Protective/Shielding Ground

2

TX

Transmit Data

3

RX

Receive Data

4

RTS

Request To Send

5

CTS

Clear To Send

6

DSR

Data Set Ready

7

SGND

Signal Ground

8

DCD

Data Carrier Detect

9

-

Reserved

10

-

Reserved

11

-

Unassigned

12

SDCD

Secondary Data Carrier Detect

13

SCTS

Secondary Clear To Send

14

STx

Secondary Transmit Data

15

TxCLK

Transmit Clock

16

SRx

Secondary Receive Data

17

RxCLK

Receive Clock

18

LL

Local Loopback

19

SRTS

Secondary Request To Send

20

DTR

Data Terminal Ready

21

RL/SQ

Remote Loopback / Signal Qualify Detector

22

RI

Ring Indicator

23

CH/CI

Signal Rate Selector

24

ACLK

Auxiliary Clock

25

-

Unassigned

 

 

 

RS232-D, RJ45 pinout

 

PT_connector_rs232rj45

 

Pin No.

Signal Name

Description

1

DSR / RI

Data Set Ready / Ring Indicator

2

DCD

Data Carrier Detect

3

DTR

Data Terminal Ready

4

SGND

Signal Ground

5

RX

Receive Data

6

TX

Transmit Data

7

CTS

Clear To Send

8

RTS

Request To Send