Adding multi-master capabilities to Interbus-S

Fieldbus technology is achieving more and more attentions throughout all the different sectors of industrial automation. They were born as local area networks dedicated to applications in the area of data acquisition and control of sensors and actuators inside the factory. Nowadays there are many fieldbus systems commercially available, and each of them is peculiar for particular kinds of applications. In this scenario the Interbus-S system is playing the role of a main character. Born under the name of the "sensor-actuator" bus, it has been appreciated by control systems designers and technicians essentially for two important qualities. Firstly, the reliability of its open-architecture, being supported by a variety of products coming from different manufacturers. Secondly, for the efficiency of its own protocol, that makes it a very interesting suite for real time applications. Notwithstanding, the architecture suffers the centralization of the mono-master arbitration scheme, which make it unsuited for a pride range of applications. Maintaining fun compatibility with the existing standard, we have studied, defined and implemented a protocol extension which overcomes these limitations and makes it ready for new scenarios.