Communication Ports
4.3 Serial Ports
Serial DB9 Port
5
1
6
9
Figure 4.3
Serial DB9 Port Pin Configuration
Mode
Pin
RS-232
RS-422
RS-485
1
Reserved (Do Not Connect)
2
RX
RX-
3
TX-
RX-/TX-
4
Reserved (Do Not Connect)
5
Common (Isolated) Ground
6
Reserved (Do Not Connect)
7
RTS
TX+
RX+/TX+
8
CTS
RX+
9
Reserved (Do Not Connect)
Shield
Chassis Ground
In RS-232 mode, ports are wired as DTE (Data Terminal Equipment). They transmit on pin 3 and receive
on pin 2.
Each RS-485 port can communicate with multiple RS-485 devices by wiring devices
together in sequence over a single twisted-pair with transmit and receive signals on
the same two wires (half duplex). For reliable, continuous communication, adhere to
the following guidelines:
• To minimize the effects of ambient electrical noise, use shielded cabling.
• The correct polarity must be observed throughout a single sequence or ring.
• The number of devices wired should not exceed 32, and total distance should be
less than 1219 m (4000 ft) at 100 kbps.
• The Common terminals should be connected to the common wire inside the
shield.
• The shield should be connected to earth ground at a single point to avoid loop
currents.
• The twisted pair should be terminated at each end of the chain.
The following shows the recommended RS485 wiring.
36
RUGGEDCOM RX1400
Installation Manual, 01/2021, C79000-G8976-1103-17
