Tailored redundancy
... with PROFIBUS periphery

Connecting periphery

Via PROFIBUS you can choose between single-sided connection (normal availability),
single-channel connection (normal availability) or switched connection (high availability).

Single-sided connection (normal availability), single-channel connection (normal availability) / switched connection (increased availability)

Connecting periphery -- Single-sided I/O connection in divided rack

PROFIBUS architecture with single-sided I/O connection

With a single connection, the I/O modules are designed with one channel and can be addressed by
both central devices.

This applies only as long as the CPU to which the I/O is connected is working correctly.


Fault tolerance
Single-sided information that is read in on only one device is available to both central devices as long as the central device that addresses the I/O is working correctly.

Connecting periphery -- Single channel I/O connection in divided rack

PROFIBUS architecture with single channel I/O connection

With a single channel connection, the I/O modules are designed with only one channel and can be addressed by both central devices.
For PROFIBUS, the single-channel connection takes place via Y link.
The Y link forms the network transition from a redundant PROFIBUS master system to a single-channel PROFIBUS DP master system.


Fault tolerance
Information that is read in on only one device is available to both central devices through the synchronization as long as the Y link is working correctly.

In the event of a fault of a CPU - the switchover of the entire I/O branch takes place bumplessly. 

Connecting periphery -- Switched I/O connection in divided rack

PROFIBUS architecture with switched I/O connection in divided rack

With a switched connection, the I/O modules are connected with both central devices via two interface modules. Both central devices are active during fault-free operation.

When writing the outputs, the data from both channels is accepted but only the data of the preferred channel is forwarded to the outputs.

Fault tolerance

The function of the system stays completely intact even if, for example, a central device and/or the connected  PROFINET network and/or one or several of the interface modules in the ET 200 connected to this network fail.

The failure of a central device can be tolerated regarding communication.

Connecting periphery -- Switched I/O connection with seperated racks

PROFIBUS architecture with switched I/O connection with seperated racks

With a switched connection, the I/O modules are connected with both central devices via two interface modules. Both central devices are active during fault-free operation.

When writing the outputs, the data from both channels is accepted but only the data of the preferred channel is forwarded to the outputs.

Fault tolerance

The function of the system stays completely intact even if, for example, a central device and/or the connected  PROFINET network and/or one or several of the interface modules in the ET 200 connected to this network fail.

The failure of a central device can be tolerated regarding communication.

Additional benefit of fault tolerance

Availability can be increased even more if both CPUs are set up completely separate from each other.

The distance between the systems can be up to 10 kilometers (16 miles).

Plant communication

With higher requirements on the availability of an overall plant it is necessary to increase the reliability of the communication, i.e. also set up communication redundantly if required.
Please see below a selection of configurations that can be used.

Plant communication -- High-available communication with standard plant bus

High-available communication with standard bus

 - via internal Ethernet interface

The bus is safety installed and not at risk of failure. Failure of one component per system will be tolerated.

Plant communication -- High-available communication with redundant plant bus

High-available communication with redundant bus

- via redundant communication processors (CPs)

The bus and the bus connection is redundantly installed. In this case, failure of the bus and one more component per system will be tolerated.

Plant communication -- High-available communication with plant bus as ring

High-available communication with ring bus

- via internal Ethernet interface


In this configuration, fault tolerance of the bus is achieved using a ring structure. Failure of one additional component can also be tolerated

Plant communication -- High-available communication with plant bus as redundant ring

High-available communication with redundant ring bus

- via redundant communication processors (CPs)

In this configuration, fault tolerence of the bus is achieved using a ring structure. Failure of one bus and one additional component can also be tolerated.