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Communication Ports
4.3 Serial Ports
Serial DB9 Port
Figure 4.3
a
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:
•
•
•
•
•
•
The following shows the recommended RS485 wiring.
36
5
1
9
6
Serial DB9 Port Pin Configuration
Pin
RS-232
1
2
RX
3
TX
4
5
6
7
RTS
8
CTS
9
Shield
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.
RS-422
Reserved (Do Not Connect)
a
a
Reserved (Do Not Connect)
Common (Isolated) Ground
Reserved (Do Not Connect)
Reserved (Do Not Connect)
Chassis Ground
Mode
RX-
TX-
TX+
RX+
Installation Manual, 01/2021, C79000-G8976-1103-17
RS-485
RX-/TX-
RX+/TX+
RUGGEDCOM RX1400
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