Special Equipment Railway Transportation Communication Net Based on the Field Bus

The special equipment railway transportation communication net based on the field bus that the paper issued, aimed at the characteristic of railway transportation, such as simple structure, distinct layer, reducing data intermediate link as far as possible in network flows , reducing the cost of entire system, increasing flexibility, reliability and the fast communication. According to this principle, the paper only adopted OSI model 1, 2 and 7 layers, and created a user layer. The structures of the transportation communication net based on the field bus are physical layer, data linking layer, application layer and user layer. On the foundation of communication net layers, we designed the communication net communication protocols based on the field bus. We set monitoring unit logic number in the data token defined in transportation communication net protocol, realized the random net of transportation task at random. RS-485 half-duplex communication net shift circuit is designed and the net experiment is as well completed.