Rockwell Automation Publication 22C-UM001J-EN-E - January 2017
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Appendix
E
Modbus RTU Protocol
PowerFlex 400 drives support the RS485 (DSI) protocol to allow efficient
operation with Rockwell Automation peripherals. In addition, some Modbus
functions are supported to allow simple networking. PowerFlex 400 drives can
be multi-dropped on an RS485 network using Modbus protocol in RTU
mode.
For information regarding DeviceNet or other communication protocols, refer
to the appropriate user manual.
Network Wiring
Network wiring consists of a shielded 2-conductor cable that is daisy-chained
from node to node.
Figure 43 - Network Wiring Diagram
Only pins 4 and 5 on the RJ45 plug should be wired. The other pins on the
PowerFlex 400 RJ45 socket contain power, etc. for other Rockwell
Automation peripheral devices and must not be connected.
Wiring terminations on the master controller will vary depending on the
master controller used and “TxRxD+” and “TxRxD-” are shown for
illustration purposes only. Refer to the master controller’s user manual for
network terminations. Note that there is no standard for the “+” and “-” wires,
and consequently Modbus device manufacturers interpret them differently. If
you have problems with initially establishing communications, try swapping
the two network wires at the master controller.
Controller
Master
PowerFlex 400
Node 1
4
5
PowerFlex 400
Node 2
4
5
PowerFlex 400
Node "n"
4
5
TxRxD+
TxRxD-
TxRxD+
TxRxD-
TxRxD+
TxRxD-
NOTE: The shield should be grounded at ONLY ONE location.
Shield
Shield
Shield
120 ohm resistor
120 ohm resistor
FRONT
PIN 8
PIN 1
