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D-sub 9 Connector Pinout

Pinout and diagram of DE9 connector (DB9 connector), commonly used for serial ports (RS-232).

Pin SIG. Signal Name DTE (PC) 1 DCD Data Carrier Detect in 2 RXD Receive Data in 3 TXD Transmit Data out 4 DTR Data Terminal Ready out 5 GND Signal Ground - 6 DSR Data Set Ready in 7 RTS Request to Send out 8 CTS Clear to Send in 9 RI Ring Indicator in

The DTE (PC) has the male connector (shown below), and the DCE (peripheral) has the female.

RS-232 Maximum Cable Length

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The maximum cable length for RS-232 is 50ft, but in practise depends on baud rate, cable specific capacitance and ambient noise. The table below contains some rules-of-thumb from experiments done by Texas Instruments years ago.

Baud rate Maximum range / cable length 19200 50ft 9600 500ft 4800 1000ft 2400 3000ft

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RS232 Pinout

Below is the pinout of a typical standard male 9-pin RS232 connector, this connector type is also referred to as a DB9 connector. A computer's serial COM port (DTE) is usually a male port as shown below, and any peripheral devices you connect to this port usually has a female connector (DCE).

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This table shows the pin numbers with signal names and the signal direction.

Pin Signal Signal Name DTE Signal direction 1 DCD Data Carrier Detect In 2 RXD Receive Data In 3 TXD Transmit Data Out 4 DTR Data Terminal Ready Out 5 GND Ground - 6 DSR Data Set Ready In 7 RTS Request to Send Out 8 CTS Clear to Send In 9 RI Ring Indicator In

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Nullmodem (9-9) Cable

Use this cable between two DTE devices (for instance two computers).

(To Computer 1). (To Computer 2).

9 PIN D-SUB FEMALE to Computer 1. 9 PIN D-SUB FEMALE to Computer 2.

D-Sub 1

D-Sub 2

Recieve Data 2 3 Transmit Data Transmit Data 3 2 Recieve Data

Data Terminal Ready 4 6+1 Data Set Ready + Carrier Detect

System Ground 5 5 System Ground Data Set Ready + Carrier Detect 6+1 4 Data Terminal Ready

Request to Send 7 8 Clear to Send Clear to Send 8 7 Request to Send Note: DSR & CD are jumpered to fool the programs to think that their online.