Connect the Modbus/Ethernet Cables
- Connect an Ethernet cable with RJ45 plug to the Ethernet port.
- Connect the Modbus cable with RJ45 plug to the Modbus port
on the PDU.
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2-wire or 4-wire shielded twisted pair cables must be used for Modbus connections. Use a cable for Modbus serial link (RJ45 to RJ45 or RJ45 to free wires depending on the Modbus controller characteristics).
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The Modbus port is optically isolated. The Modbus port’s ground is not connected to any other ground.
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Install 150 Ohm termination resistors at each end of each bus if the buses are very long and operate at high data rates. Busses under 610 meters (2000 feet) at 9600 baud or under 305 meters (1000 feet) at 19.200 baud should not require termination resistors.
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Install 400–650 Ohm bias resistors at or inside the system controller; one from D0 to ground and one from D1 to +5 VDC.
Example: Modbus 4–Wire on RJ45 Connector
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- If needed, use the pass-through communication port on the roof of the PDU as an extension of either the Modbus or the Ethernet port. Use a standard UTP straight-through cable with RJ45 plugs, connect one end to the intended port on the PDU, and the other end to the port on the roof (from the inside). Then, connect the external Modbus with RJ45 plug or Ethernet cable with RJ45 plug to the extension port on top of the PDU.
- If more than one PDU must be connected to the Modbus controller,
use an RJ45 Modbus hub or splitter block.NOTE: Wiring should be done in accordance with local wiring codes. Route signal cables separately from power cables to reduce noise.