...many technicians considering implementing an industrial network imagine connecting their PLCs via TCP/IP to the Internet and comfortably interacting with their show system from home or office computers. Standalone PLCs are rarely "network-ready." Because of the many different types of networks most manufacturers make several adapters. PLCs on a network are assigned node numbers or addresses identifying them to the other devices on that network. It is possible for modern industrial networks to be based on the TCP/IP (Transmission Control Protocol/Internet Protocol) protocols, and many technicians considering implementing an industrial network imagine connecting their PLCs via TCP/IP to the Internet and comfortably interacting with their show system from home or office computers. While technically possible, this is not generally desirable. Most PLC manufacturers offering TCP/IP options allow configuration and monitoring via Web browser, but I can see potential problems with opening access to an industrial network to the Wold Wide Web. I would also have significant reservations concerning the reliability of the network if it were connected to the university or company backbone and subject to sporadic slowdowns and bandwidth saturation. Imagine a denial of service attack on your show! Implementation of TCP/IP networks in industrial situa- tions generally are used for applications where isolated intranet-connected computers communicate with PLCs gathering data for materials ordering, maintenance needs or productivity reporting. Wiring and connection limitations typical of personal computer networks apply. EthernetIP is the open standard for industrial automation applications making use of ethernet and TCP/IP. Another popular network protocol is DeviceNet based on the Controller Area Network (CAN) protocol developed by Bosch for the European automotive market. DeviceNet is wired in a buss shape and it's an open standard protocol. Devices built to the DeviceNet standard are offered by a multitude of manufacturers and all are designed to work together. DeviceNet is based on a Producer/Consumer network model, where any node (device) can produce or use information, allowing for more efficient peer-to-peer communications. Even simple devices like pushbuttons are manufactured with DeviceNet interfaces, greatly reducing wiring and installation costs. DeviceNet networks are limited to 64 nodes, over 1600 feet of cable transferring data at speeds of up to125K bits/second. TD & T S U M M E R 2 0 0 3 51