4 modbus connections, 5 diagnostic connection, 6 wiring rules - modbus networks – GE GEH6505A User Manual
Page 10: Chapter 2 – installation, Power leader™ ethernet gateway, 2–4 modbus connection, 2–5 diagnostic connection, 2–6 wiring rules – modbus networks
POWER LEADER™ Ethernet Gateway
Chapter 2 – Installation
2–4 Modbus Connection
The Modbus RTU networks should be connected to
the RS485 ports on the back of the Ethernet
Gateway, as shown in Figure 9.
Figure 9. Connecting an RS485 network to the Ethernet
Per the EIA-485 standard, the RS485 networks must
be terminated at both ends. Position the Ethernet
Gateway at one end of the RS485 networks, as it is
internally terminated. The user must ensure that
the final device on each network is terminated
correctly, as shown in Figure 10.
Figure 10. Terminating an RS485 network at the last device.
2–5 Diagnostic Connection
The RS232 port on the back of the Ethernet
Gateway is provided for connection of a dumb
terminal to the Gateway. The terminal may be used
for configuring the Ethernet Gateway’s settings or
for diagnostic purposes. For diagnostic purposes,
the Gateway may be set to display all messages and
traffic on the terminal so that problems may be
tracked down and corrected. To connect a terminal
(usually a laptop computer running Windows’
Terminal accessory software) to the Gateway, plug
its RS232 cable into the RS232 port on the back of
the Ethernet Gateway, as shown in Figure 11.
Figure 11. Connecting a dumb terminal to the RS232 port.
2–6 Wiring Rules – Modbus Networks
When wiring Modbus RTU devices to an Ethernet
Gateway, follow the wiring rules below to ensure
proper configuration. Refer to GEH-6502, the PMCS
Network Architecture Guide
, for specific examples of
correct and incorrect configurations.
1. Up to 31 Modbus devices may be attached to a
single Modbus network. RS485 repeaters do not
have Modbus addresses, but do count as devices
toward the 31 physical devices per network limit.
2. Every device on a single Modbus network must
have a unique address. (Devices on different
networks may use the same Modbus address,
i.e., it is acceptable to have a device addressed as
device 10 on Network 1 and another device
addressed as device 10 on Network 2.) Use the
Modbus address worksheets (at the end of this