A dual media industrial LAN for real time applications

To integrate process control instrumentation consisting of programmable logic controllers and PCs, an industrial network is being designed as a backbone for communication. The design of the hardware and software is discussed focusing on the arbitration, redundancy, and interface problems. To provide real-time features, a mini MAP 3.0 architecture was selected. It supports media access protocols with deterministic access, with the upper layer software for logical link control and the application layer directly utilizing these services. The system was developed around this architecture. The hardware development involves intelligent LAN controllers with different backplane bus interfaces. All communication tasks were taken over by the network controllers with an interface to physical media on one end and to the host on the other side. The dual media were chosen so that transmission will always be on both media, and when a cable fault occurs the reception of the data will be switched over from the faulty medium to the healthy one.<>