Real-Time Fieldbus Communications Using Profibus Networks
Ref: HURRAY-TR-9823 Publication Date: Dec 1999
Real-Time Fieldbus Communications Using Profibus NetworksRef: HURRAY-TR-9823 Publication Date: Dec 1999
This paper provides a comprehensive study on how to use Profibus fieldbus networks to support real-time industrial communications, that is, on how to ensure the transmission of real-time messages within a maximum bound time. Profibus is based on a simplified Timed Token (TT) protocol, which is a well-proved solution for real-time communication systems. However, Profibus differs with respect to the TT protocol, thus preventing the application of the usual TT protocol real-time analysis. In fact, real-time solutions for networks based on the TT protocol rely on the possibility of allocating specific bandwidth for the real-time traffic. This means that a minimum amount of time is always available, at each token visit, to transmit real-time messages. Conversely, with the Profibus protocol, in the worst-case, only one real-time message is processed per token visit. We propose two approaches to guarantee the real-time behaviour of the Profibus protocol: an Unconstrained Low Priority Traffic profile and a Constrained Low Priority Traffic profile. The proposed analysis will show that the first profile is a suitable approach for more responsive systems (tighter deadlines), whilst the second allows for increased non-real-time traffic throughput.
Published in IEEE Transactions on Industrial Electronics, IEEE IES, Edited: L.
Jain, Volume 46, Issue 6, pp 1241-1251.
Real-Time Fieldbus Communications Using Profibus Networks (30, Dec, 1899 Outdated)