Machine Design

Profibus goes real-time

The Profibus trade organization has announced a Profinet real-time extension for general automation applications. A second Profinet real-time extension is also under way for high-performance motion-control applications.

Soft Real Time (SRT), a currently available version, has cycle times of 5 to 10 msec and meets the demands of factory automation. It is also compatible with TCP/IP Ethernet protocol. Run-time software can be downloaded from

Currently under development for motion-control applications is Isochronous Real Time (IRT). It will be able to control up to 150 axes with a cycle time of 1 msec and jitter of less than 1 msec. IRT will use next-generation switching technology and a four-port real-time ASIC switch for implementing IRT in products. An ASIC switch allows interrupt-free redundant solutions for complex applications at low cost. The objective includes porting the Profibus motion-control profile largely unchanged to Profinet as an important contribution to protecting existing Profibus investments.

The first certified Profinet products include a gateway from Hilscher and an industrial Ethernet/Profibus link and a Profinet communications processor from Siemens. Profinet Technology and Application Guides are available at, or request a hard copy from the Profibus Trade Organization.

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