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RS232串口DB9管脚定义及在不同波特率下通信线缆最大长度

D-sub 9 Connector Pinout(DB9管脚定义)

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(在不同波特率下串口线最大长度)

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(15米)
9600 500ft(150米)
4800 1000ft(300米)
2400 3000ft(900米)

Questions, comments ==> info (at) (this domain)

与MAX232连接方式如下:

如果采用公头,连接方法是:MAX232(14,7)连接公头(3),MAX232(13,8)连接公头(2)

如果采用母头,连接方法是:MAX232(14,7)连接母头(2),MAX232(13,,8)连接公头(3)

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