194 ï Fieldbus CommunicationETHERNETWAGO-I/O-SYSTEM 750Linux Fieldbus Coupler10Base-T, 100BaseTXEither the 10BaseT standard or 100BaseTX can be used for the WAGOETHERNET fieldbus node.The network architecture is very easy and inexpensive to assemble with S-UTP cable as transmission medium or with cables of STP type.Both types of cable can be obtained from any computer dealer.S-UTP cable (screened unshielded twisted pair) is single-shielded cable ofCategory 5 with overall shield surrounding all twisted unshielded conductorpairs and an impedance of 100 ohm.STP cable (shielded twisted pair) is cable of Category 5 with stranded andindividually shielded conductor pairs; no overall shield is provided.Wiring of the fieldbus nodesMaybe, a crossover cable is required for direct connection of a fieldbus nodeto the network card of the PC.Fig. 10-2: Direct Connection of a Node with Crossover Cable g012906dIf several fieldbus nodes are to be connected to a network card, the fieldbusnodes can be connected via an ETHERNET switch or hub with straightthrough/parallel cables.Fig. 10-3: Connection of a Node by means of a Hub with Parallel cables g012908dAn ETHERNET switch is a device that allows all connected devices totransmit and receive data with each other. The switch can also be viewed as aìdata traffic copî where the hub ìpolicesî the data coming in and going out ofthe individual ports, so the data will only be transmitted to the required node.WAGO recommends using a switch rather then a hub, this will allow for amore deterministic architecture.
