Entry type: FAQ, Entry ID: 13595393, Entry date: 02/04/2008

How do you connect an operator panel (ProTool) to an H system (S7-400H)?

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An operator panel can not be connected directly to an H controller with the same address, because the addresses on the bus and the assignments are not unique.

Fig. 01

The connection of operator panels - except Push Button Panels - to an H controller via a Y link is not released. More information on connecting a Push Button Panel to an H system via Y link is available in Entry ID: 15263039.

Below are a number of examples of how to connect an operator panel to an H controller.

  1. Connect an operator panel to multiple controllers
  2. Connecting operator panels unilaterally
  3. Connecting operator panels redundantly
  4. Connect operator panels in switched configuration

1. Connect an operator panel to multiple controllers
In this version the operator panel is connected to both controllers via a bus.

If the operator panel is assigned to multiple CPUs, the CPUs must have different addresses.

Fig. 02

However, in this configuration, if a CPU fails on the operator panel, there is always an error message when an attempt is made to access the data on the failed device. This blocks the operator panel. This is a system behavior of TDs, OPs, TPs and PPs that can be configured with ProTool.

2. Connecting operator panels unilaterally
The operator panel is connected only to one subsystem. If the CPU of this subsystem fails, it is no longer possible to operate.

Fig. 03

In this version we recommend using a Mobile Panel. There must also be a connection box for the Mobile Panel in each bus system of the two controllers.

3. Connecting operator panels redundantly
The "simplest" option is to connect an operator panel to each of the two subsystems. This option best complies with the principle of redundancy, because the hardware is duplicated. 

Fig. 04

4. Connect operator panels in switched configuration
One or more operator panels and each of the subsystems of the S7-400H are connected a separate

Repeaters are used to achieve this splitting up into separate segments. By disconnecting the repeater concerned via the power supply, only one segment appears to the operator panel on the controller side and therefore only one CPU. The same address must be set on both CPUs. 

Fig. 05

The data comparison that the S7-400H operating system makes between the subcontrollers ensures that the data is identical in both subsystems after switchover. Upon each input via the operator panel the operating system "distributes" the data practically simultaneously in both systems.

The power supply can be connected to the repeaters via "changeover switches", for example. This means that only one repeater is connected to the power supply at any one time. The switchover can be made manually via a switch or automatically upon CPU switchover via digital outputs. Since when the first repeater is disconnected, the internal terminating resistor is not effective, you need an active terminating resistor.

Fig. 06



Repeater  6ES7 972-0AA01-0XA0
Active terminating element 6ES7 972-0DA00-0AA0

Settings in STEP 7:
The two subcontrollers must have the same MPI or PROFIBUS address for this configuration.
In the case of integrated projects, the operator panel must not be connected to the relevant subnetworks.

Connection setup for operator panels to the S7-400 CPU:
In principle, for connection setup of the operator panel to an S7-400 CPU via MPI/PROFIBUS the rack number of the subrack, the slot and node address are checked. Both controllers of the H system always have different rack numbers. In ProTool, when configuring a connection with MPI/PROFIBUS, you must assign a unique rack number.

For the operator panel - see Fig. 7 - to set up a connection to both CPUs a zero must be entered for the "Expansion Slot" and "Rack". Then, regardless of the rack and slot, a connection is set up to the CPU which the operator panel finds from the node address specified.

If the ProTool project is integrated in the STEP 7 project, the operator panel must not be connected to the corresponding subnets in NetPro.
If difficulties with communication arise when configuring with PROFIBUS DP, you must recalculate the network parameters.
The operator panels connected via the "switched" repeater must be configured on a different DP segment of the CPU to "other nodes" (default nodes).

Communication setting under ProTool:

  • The ProTool project does not have to be integrated into the STEP 7 project. The configuration can be made "outside" the complete STEP 7 H project.
  • When parameterizing the operator panel you must enter Slot 0 and Rack 0 of the communication partner so that a connection can be set up between the operator panel and the CPU.
  • The MPI/PROFIBUS address of the operator panel and the controller must be unique.

Fig. 07