19 December 2008
Certification is a decisive factor contributing to user acceptance of supplied safety solutions. Nowadays, safety-related field devices (F-slave/F-device) communicate via the Profisafe protocol, and their proper functioning is verified by means of a certification test. Certification of Profibus DP slaves and Profinet IO devices has been an established practice for five years. Now, PI (Profibus & Profinet) is also providing certification for safety-related hosts (F-Hosts).
The Profisafe host is a software package that runs on the processing controller. This software can be used in identical form on different controllers.
A prerequisite for performing a Profisafe host test is the existence of a Profibus or Profinet certificate for the controller in which the Profisafe host is integrated (basic test). The Profisafe host test itself, which is approved by TÜV, is virtually an automated test performed at accredited test laboratories. As part of this process, the parameters, watchdog, and GSD files are tested first, followed by negative tests in the interface module, a Profisafe profile test, and the interoperability test in the test equipment. In addition, the program has built-in protection mechanisms. A CRC (cyclic redundancy check ) is used to protect Profisafe host programs thus enabling TÜV to detect changes. The CRC protection encompasses the Profisafe host project, the test case scripts, and the test result. This enables TÜV to detect test case changes and to check whether the test was implemented completely. PI provides a Profisafe certificate based on a positive test report confirming the conformity of the host.
The advantages to the user are obvious: When products with a Profisafe certificate are used, the residual error probability in data transmission is no longer a concern because this has already been proven generally for all proper implementations of Profisafe. In addition, all deterministic error models have been handled as part of the Profisafe stack certification.
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