Connecting Multiple Rs485 Devices - RuggedCom SIMATIC NET RS416PF Equipment Manual

Communication Ports
4.6 Connecting Multiple RS485 Devices
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4.6

Connecting Multiple RS485 Devices

Each RS485 port can communicate with multiple RS485 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:
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The following shows the recommended RS485 wiring.
2
1
1
2
3
4
5
32
Red – Error
Off – No signal detected
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.
3
4
RUGGEDCOM RS416PF
Common (Isolated Ground)
Negative
Positive
Shield to Earth (Connected At a Single Point)
5
5
120Ω 10nF
120Ω 10nF
6
RUGGEDCOM RS416PF
Equipment Manual, 10/2023, C79000-G8976-1355-07