Interoperability of the new Generation – The How and What


PLCopen and OPC Foundation combine their technologies to a platform and manufacturer Independent information and communication architecture. This mix of OPC Unified
Architecture (UA) and IEC 61131-3 creates interesting options for the realization of automation structures.
Goal #1: Semantic Interoperability by mapping IEC61131-3 into OPC UA Namespace

The first goal was to map the IEC 61131-3 software model to an OPC UA information model.
This goal can be described in the following way: when today an IEC 61131-3 control program
is loaded on different control platforms from different control suppliers one can communicate
with these controllers by using OPC UA and access process variables. The representation in
the namespace of the OPC UA servers is however different for each platform: A visualization
program must each time be adapted for each controller although the control code is identical.
However, the expectation from the customers is that an identical control project also is
accessed via OPC UA in the same way. Besides the accessibility to the instances of the
controller variables, further metadata needs to be available. Descriptions how complex data
structures are constructed, the type of function blocks used, and which variable are in or out
parameters. Other metadata can be the number of tasks and their cycle times. The entire IEC
61131-3 software model and the content of the controller programs are mapped into the OPC
UA namespace. This namespace can be provided by an OPC UA server which is integrated
into an embedded controller.

But why use OPC UA? With the Unified Architecture, OPC Foundation answers questions

  • How to find a communication partner?
  • How are data, metadata, and functionalities of the communication partner made available?
  • How can communication be reliable, performant and independent of the operating system
    or the programming language?
  • How can security aspects such as authentication and encrypting be ensured?

Unified Architecture offers the basis for universal, secure and durable network
communication, i.e. provides the monitoring of configurable timeouts and connecting
interrupts, encrypted communication and different communication protocols, are part of OPC
UA. Many other organizations use OPC UA as a modern and efficient transport layer.
PLCopen quickly recognized the possibilities, and adds to OPC UA by describing the
contents, thus „what “, which should be exchanged: not only variables but also functions and
metadata of the control logic.
The results from the working group are an important basis: A HMI for example
can now provide a picture template for a function block – this graphic element can now
communicate directly with all controllers on which the function block is present. This clearly
simplifies the engineering process.

The specification “OPC UA Information Model for IEC61131-3” has been released on March 24th, 2010.

Goal 2#: OPC UA CLIENT FOR IEC 61131-3 (PLCopen)
The interaction between IT and the world of Automation is certainly not revolutionary, but is based on the long-established model of the automation pyramid: The upper level initiates a data communication (as a client) with the level below, which responds (as server)
cyclically or event-driven: A visualization, for example, can request status data from the PLC or
transfer new production recipes to the PLC. With Industrie 4.0 this strict separation of the levels
and the top-down approach of the information flow will start to soften and mix: In an intelligent Network each device or service can autonomously initiate a communication with other Services.

In collaboration with the OPC Foundation, the PLCopen has defined corresponding OPC-UA
client function blocks. In this way the controller can play the active, leading role, in addition or as an alternative to the usual distribution of roles. The PLC can thus horizontally exchange complex data structures with other controllers or vertically call up methods in an OPC-UA server in an MES/ERP system, e.g. to retrieve new production orders or write data to the cloud. This enables the production line to become active autonomously – in combination with integrated OPC-UA security a key step towards Industrie 4.0.

The updated v1.1 specification “PLCopen OPC UA Client for IEC61131-3” has been released on September 5th, 2016.

OPC and PLCopen collaboration means that OPC UA can be implemented in an environment that features the well-known IEC 61131-3 programming standard from PLCopen.
This results in the consistent use of OPC UA components.

Companies behind

  • 3S-Smart Software Solution
  • ABB
  • Ascolab
  • BECKHOFF Automation
  • Bosch Rexroth
  • B&R Industrie-Elektronik
  • Fuji Electric
  • General Electric Corporation (GE)
  • HIMA
  • Honeywell
  • Hochschule Harz
  • Mitsubishi Electric Europe
  • OLDI/Softing
  • Omron Corporation
  • OPC Foundation
  • Phoenix Contact GmbH
  • PLCopen
  • Rockwell
  • Siemens AG
  • Wago

More Information, Specification, Videos, Success stories

  • See here: OPC UA & PLCopen Collaboration in 4min (short overview)
  • See here: OPC UA & PLCopen Collaboration in 15min (more details)
Success stories
    • Download here: Water Treatment solution with PLCopen OPC UA Client for IEC61131-3
    • Download here: Smart meter solution with PLCopen OPC UA Client for IEC61131-3

About PLCopen

PLCopen is an independent organization providing efficiency in industrial automation based
on the needs of users. Its members, representing various industries, focus on harmonization of
control programming, and application and interfacing engineering. Founded in 1992, PLCopen members have concentrated on technical specifications around IEC 61131-3, creating specifications and implementations in order to reduce cost in industrial engineering. The outcome for example is standardized libraries for different application fields, harmonized language conformity levels and engineering interfaces for exchange. Experts of the PLCopen members are organized in technical committees and together with end users define such open standards.