PROFIsafe to improve distributed safety: Herbert Barthel and Dr. Wolfgang Stripf of Siemens describe developments to the PROFIBUS specification that have seen the introduction of PROFIsafe-a safe transmission method. (Profisafe).

Publication: Embedded Systems

Publication Date: 01-NOV-02

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COPYRIGHT 2002 CMP Information Ltd.

PROFIsafe, the safe transmission method using PROFIBUS DP and its range of transmission technologies, such as RS 485 (main area: production), MBP-IS (1) (main area: process) and optical fibre, has passed the acid test in comprehensive applications up to SIL3, AK6 and Category 4. So what has happened since the first publication of the PROFIBUS Specification V1.0 at the Hanover Trade Fair 1999? Which devices are now available/being developed? How is market acceptance of the new functions? What is the current situation with regard to global regulations and standards? What findings have been made concerning inspections and testing and certifications? Is PROFIsafe being further developed?

As the way the method works has already been explained in many publications--see Reference 1, this article will only touch on the main points. PROFIsafe is based on the polling principle of PROFIBUS between a master and its assigned slaves and assumes an encapsulation of the safety measures in the communication stations, i.e. the standard PROFIBUS with its ASICs, cables, plugs etc. is implemented exactly as before. PROFIsafe uses four measures to safeguard against possible errors during the transmission of messages, such as incorrect addressing, loss, delay, etc: continuous numbering of PROFIsafe data, time monitoring, authenticity monitoring by means of 'passwords' and an optimized CRC fuse.

Implementation of PROFIBUS in production with high response times as well as in hazardous areas of the process industry with minimum power losses places high demands on the flexibility of realization in field devices, which include laser scanners, light grids, drives, robots, cut off valves, overcharge fuses, gas detectors, etc. As most modern devices use microprocessors, it made sense to use software to implement the PROFIsafe method.

The operating conditions...

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