MAN0923_Issue 3_04/15
Touchpoint Pro
Operating Instructions
180
14.2.3 Electrical connections
The electrical connections are shown below:
Modbus RTU Interface
Terminal
TB6
TB7
1
A1 IN
A2 IN
2
B1 IN
B2 IN
3
A1 OUT
A2 OUT
4
B1 OUT
B2 OUT
5
Drain TB6
Drain TB7
Note: The respective IN and OUT terminals are connected together internally, i.e. A1 IN is connected to
A1 OUT
14.2.4 Configuration Examples
The Modbus interface consists of two independent Modbus ports. The RS485 connections are located on
terminals TB6 and TB7 of the Control Module. For convenience, IN and OUT terminals are provided which
are connected together internally.
The diagram below gives example configurations of which the second and third offer redundancy:
14.2.5 Termination resistor
If the Touchpoint Pro is the last node in a Modbus system highway, it is necessary to connect a termination
resistor between A and B, to avoid reflections on the RS485 circuit.
For convenience, Touchpoint Pro has a set of jumpers which will switch a 120
Ω
resistor across the
connection. In this case, the RS485 IN and OUT terminals are no longer connected together internally, and
the OUT terminals are floating. Only the IN terminals should be used.
Note: The default configuration for the jumpers is with the termination resistance off.
14. Appendix 1 - Modbus Option