RS485 (serial)
An RS485 connection supports Modbus RTU protocol. Using this connection type, the
Gateway is wired to an RS485 bus which typically leads to a serial I/O card or Modbus I/O
card (see Figure 5-2). Up to 31 Gateways can be connected to a single I/O card in this
manner.
Figure 5-2: RS485 Architecture
A. Engineering station
B.
Primary control network
C. Controller and I/O
D. Secondary control network
E. Serial I/O card
F. RS485 bus
G. Wireless Gateway
5.3 Modbus
®
The Gateway supports both Modbus RTU over the RS-485 serial port and Modbus TCP over
Ethernet. It functions as a sub device on the Modbus network and must be polled by a
Modbus master or client (host system).
Communication settings
It is import that the Modbus communication settings in the Gateway match the settings in
the Modbus master or client. Please refer to host system documentation for more
information on how to configure these settings. The Modbus communication settings can
be found by navigating to System Settings → Protocols → Modbus.
Operation and maintenance Reference Manual
May 2020 00809-0600-4410
40 Emerson.com
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