LAN stress management

It is noted that increasing numbers of operator interface packages attached to programmable controllers through local area networks (LANs) can stress communications if not properly used. The author demonstrates design practices intended to improve throughput to display panels while decreasing communications to controllers. The result of less activity on the network will also boost the scan speed of controllers, which have to do the real work. This is done by careful planning of the communication tasks. Ordinary techniques of using mailboxes in an intermediate device, as well as updating by exception through the use of ladder logic are used.<>