Siemens RUGGEDCOM RX1400 Installation Manual page 38

Chapter 3
Communication Ports
b
In RS-232 mode, ports transmit to DTE (Data Terminal Equipment) devices on pin 2 and receive from DTE devices on pin 3.
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.
2
1
Figure 18: Recommended RS-485 Wiring
1. RUGGEDCOM RX1400 Device 2. Common (Isolated Ground) 3. Negative 4. Positive 5. Shield to Earth (Connected At a Single
Point) 6. RS-485 Devices (32 Total)
28
3 5
4
120Ω 10nF
Pin
RS-232
9 Reserved (Do Not Connect)
Shield
5
120Ω 10nF
RUGGEDCOM RX1400
Installation Guide
Mode
RS-422 RS-485
Chassis Ground
6
Serial Ports