Understanding the IEC 61499 Runtime Environment and the 4DIAC Framework

As described by IEC 61499, applications built with this standard use function blocks (FBs). While FB creation methods exist, the actual execution of FB networks on physical devices requires a runtime environment that loads the network, processes events, and follows the standard’s rules.

The standard itself does not specify where the runtime environment resides; it merely defines how distributed industrial systems should be developed, leaving the implementation to developers. This creates a conceptual gap between application design and execution.

The top rectangle in the diagram represents the IEC 61499 system model, which you create with a tool that allows you to design FBs and connect them, as well as map parts of the application to specific devices. The large lower block represents actual hardware such as PLCs, Raspberry Pi, or other controllers where the runtime must run, receiving the FB network from the design tool, executing it, and handling events between blocks.

The 4DIAC framework provides two projects to develop IEC 61499‑compliant distributed control systems: 4DIAC‑RTE (FORTE) , a lightweight portable C++ runtime that runs on embedded devices and various operating systems (Windows Cygwin, Linux, NetOS, VxWorks, etc.), and 4DIAC‑IDE , a Java/Eclipse‑based integrated development environment for modeling FBs, applications, and device configurations, which can export FBs to C++ code for FORTE.

Because FORTE runs on headless PLCs, graphical user interfaces (HMIs) are not directly supported; instead, the article recommends using the Function Block Development Kit (FBDK) from Holobloc, a Java‑based IEC 61499 framework that provides an HMI runtime (FBRT) and can be launched from 4DIAC‑IDE, offering graphical blocks not available in FORTE.