FieldBus-Real-time comes to OSI

The authors describe FieldBus, the activity initially responsible for the creation of communications standards suitable for time-critical automation system use. The authors focus on time-critical communications and on new standards and alternatives to the open system interconnection (OSI) seven-layer stack to support time-critical applications. Automation vendors and users are the driving force behind the development of the new standards for time-critical communications, because their control systems are the current preeminent users of time-critical networks, and because market forces are necessitating the conversion from currently-existing proprietary networks to an open system where products from different vendors all intercommunicate. The standards support a mix of time-critical and informational traffic, both to provide for current time-critical functions and to integrate with the general OSI informational networks which are commonly required in factory management applications. The first set of such de jure standards supporting the FieldBus sensor-controller-effector architecture is now starting to emerge