The influence of PROFIBUS message block time on transmission delay time property

The real time property of fieldbus is very important to industrial control system. The transmission time delay is an important factor that influences the real time property of fieldbus. Starting from the medium access control mechanism of PROFIBUS, the PROFIBUS simplified transmission time delay formulas were given, and one of the important factors that influence message transmission time delay-message block time, has been deeply analyzed. According to the relation of the address of the node which tries to send message with the node which owns the token, PROFIBUS message block time mathematical model was proposed, and the correctness of the mathematical model has been validated by the simulation. The conclusion of this paper will provide the theoretic reference basis for the further study on the real time property of PROFIBUS.