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INTERBUS is designed as a fast bus for the transmission of process data in industrial environments. Due to its transmission method and topology, INTERBUS offers outstanding performance features such as fast, cyclic, and time-equidistant transmission of process data. INTERBUS-Safety is a functional extension of this proven bus system for the transmission of safety-related data.

INTERBUS-Safety protocol

INTERBUS-Safety protocol  

INTERBUS-Safety protocol

INTERBUS-Safety extends the INTERBUS system by adding the option of safe data exchange. Freely programmable safety functions can be executed with the system on a safe controller and the required safe input and output data can be transmitted from and to the safe INTERBUS devices.

The safe controller and the safe INTERBUS devices communicate with one another via the INTERBUS-Safety protocol, which is superimposed on the standard INTERBUS protocol and contains the safe input and output data as well as data security information.

Black channel principle

Black channel principle  

Black channel principle

The black channel principle used with INTERBUS-Safety ensures that safe data is transmitted via a standard network. The bus system therefore does not perform any safety-related tasks, it only serves as a transmission medium.

Safe and non-safety-related data is integrated into the data flow of the summation frame protocol of INTERBUS. Only safe INTERBUS devices and the safe INTERBUS controller can evaluate the inserted safety protocol.

The INTERBUS-Safety protocol includes measures for protecting the safety-related data, which detect the following errors:

  • Repetition of messages
  • Loss of messages
  • Insertion of messages
  • Incorrect order of messages
  • Destruction of messages
  • Delay of messages
  • Mix up of devices

In addition, the deterministic processing of the INTERBUS-Safety protocol means the response time can be observed via a given safety chain, i.e., from the input, safe transmission, and processing to the output.

Response times

Short response times with the INTERBUS-Safety system  

Short response times with the INTERBUS-Safety system

The INTERBUS-Safety system features short response times and guaranteed shutdown times. Safety processes are sequences that must be able to initiate shutdown within a very short time.

In many cases, only a short time elapses between detecting a dangerous intervention and the required shutdown. Due to the high efficiency of the summation frame protocol, the INTERBUS system provides very short response times at a low clock rate.

The cycle times for INTERBUS can be calculated in detail thanks to deterministic protocol processing. For each safety function, a fixed length of time – the guaranteed shutdown time – elapses for the signal flow from the input terminal block to the output terminal block. The guaranteed shutdown time is based on the longest processing time of the inputs involved in the safety function and the parameterised shutdown time of the output involved and is therefore specific to each safety function.


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