3.1 Modbus RTU Cable
The Modbus RTU cable should be Belden 3105A (22 AWG) or similar shielded data communication cable connected to a
router operating at 4800 Baud minimum (>9600 Baud preferred).
3.2 Modbus TCP Cable
The Modbus TCP cable should be CAT 5/5E or higher shielded data communication cable suited to the installation
distance and ambient environment factors.
Spurs shall not be longer than 1m each, and shall not exceed 10m combined total length.
The maximum cable length without line repeaters is 1.2km (1200 m, 1300 yd).
The maximum wire size is 1.5 mm
3.3 Modbus RTU and TCP Electrical Connections
The electrical connections are shown below:
Some transceiver manufacturers have been known to incorrectly reverse their RS485 Data terminals, which can
cause Tx/Rx to fail. If this happens, simply swap over the TPPL's A and B cables and then re-test.
Note: You should connect a 120Ω termination resistor (R
TPPL is the last node in a Modbus system highway.
Note: The external R
Pt. No. 3011M5027_1
Modbus RTU Connections
is not needed if the logic solver side has an internal R
) between A and B to prevent reflections on the RS485 circuit if
Modbus Installation Guide