RUGGEDCOM RMC20
Installation Guide
Chapter 3
Communication Ports
RS485/422 Data Ports 17
In adherence to the EIA/TIA guidelines for RS232 communications, the following is recommended by Siemens:
• Always use shielded cabling to minimize the effects of ambient electrical noise
• Although greater distances are possible, limit the cable length to 15 m (49 ft) or less for more reliable
communications
• Use a baud rate of 120 kbps
The RS232 port uses a Phoenix-style DB9 compression connector. The following is the pin-out for the connector:
Figure13:Phoenix-Style DB9 Connector Pin
Configuration
Pin Name Description
1 Reserved (Do Not Connect)
2 RD Receive Data
3 TD Transmit Data
4 Reserved (Do Not Connect)
5 SGND Signal Ground
6 Reserved (Do Not Connect)
7 Reserved (Do Not Connect)
8 Reserved (Do Not Connect)
9 Reserved (Do Not Connect)
Section3.2.2
RS485/422 Data Ports
The serial terminal includes a single RS485/RS422 data port. In half duplex mode, the RS485 connections (Rx+,
Rx-, COM) should be connected. In full-duplex mode, the RS422 connections (Rx+, Rx-, Tx+, Tx-, COM) should
be connected. Both RS485 and RS422 can accommodate multi-drop networks, for master-slave serial network
communications. For both RS485/RS422 connections, the following general guidelines should be followed:
• 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 (typically with a 120 Ohm resistor and a 10nF
capacitor in series across the twisted pair).
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