Modbus Rtu Cable; Modbus Tcp Cable; Modbus Rtu And Tcp Electrical Connections - Honeywell TPPL Modbus TCP Installation And Setup Manual

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.
In addition:
• 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
MAN0995_Iss 1_01/16
Pt. No. 3011M5027_1
M
ODBUS
(15 AWG).
2
MODBUS RTU Label
Drain D
Data + A (D+)
Data - B (D-)
Figure 3. Modbus RTU Connections
is not needed if the logic solver side has an internal R
T
I
NSTALLATION
Caution
Terminal ID Logic Solver
1
2
3
) between A and B to prevent reflections on the RS485 circuit if
T
.
T
8
D
A (D+)
B (D-)
Touchpoint Plus
Modbus Installation Guide