Open-ness and IEC 61131-3

It is becoming common now to consider the whole of the supply chain, not just the make/production area. Also, we are moving away from the centralised proprietary systems towards distributed open systems. This is true not only for acquisition and control systems but those embracing safety as well. One of the prime aims of IEC 61131-3 is to provide a common way of programming a wide range of devices - PLCs, distributed control systems (DCSs), board-level products and fixed-functionality products. It has achieved a wide acceptance in these areas but, unfortunately, the lack of definition on code generation and target environments plus the lack of sufficiently comprehensive conformance tests have not allowed this prime aim to work fully. This paper looks at a pragmatic way of using the standard that is to choose one of the 61131 tools that satisfy a set of criteria. These criteria are set out in relation to the changing architectures.