A real-time semantics for the IEC 61499 standard

Abstract

Abstract-The IEC 61499 standard provides an executable model for distributed control systems in terms of interacting function blocks. However, the current IEC 61499 standard lacks appropriate timing semantics for the specification of timing requirements, reasoning on timing properties at the model level, and for the timing verification of a specific deployment.In this paper we address this fundamental shortcoming by proposing Real-Time-4-FUN, a real-time semantics for IEC 61499. The key property is the preservation of non-determinism, allowing us to reason on (and verify) timing properties at the model level without assuming any specific scheduling policy or stipulating specific order of execution for the deployment. This provides for a clear separation of concerns, where the designer can focus on properties of the application prior to, and separately from, deployment verification. The proposed timing semantics is backwards compatible to the current standard, thus allow for reuse of existing designs. The transitional property allows timing requirements to propagate to downstream sub-systems, and can be utilized for scheduling both at device and network level.Based on a translation to RTFM-tasks and resources, IEC 61499 the models can be analyzed, compiled and executed. As a proof of concept the timing semantics has been experimentally implemented in the RTFM-core language and the accompanying (thread based) RTFM-RT run-time system.

IEC 61499 Runtime Environments: A State of the Art Comparison

“…RTFM-RT is a RTE for the IEC 61499 built on the RTFM core language [10]. It is using the Event Chain concept and implements them as synchronous task chains [11]. The RTE is mostly build for real-time research.…”

RTFM-RT: A threaded runtime for RTFM-core - towards execution of IEC 61499

“…It has the goal of facilitating embedded development and concurrent programming in general by giving guarantees for execution and compile-time timing analysis. The work in [8] proposes a real-time semantics to the IEC 61499 standard based on the RTFM-MoC. It details the mapping of timing requirements from IEC 61499 programs to the timed task and resource model of RTFM-core.…”

“…Furthermore, asynchronous events may not reoccur before their associated tasks are dispatched, which is ensured by timing analysis. With the outset from RTFM-core an additional extension to IEC 61499 would allow schedulability and response time analysis, i.e., adding timing properties and constraints to synchronous event chains [8]. Previous work relied on the SRP [9] based RTFM-kernel to ensure deadlock free execution.…”

Abstract timers and their implementation onto the ARM Cortex-M family of MCUs

“…Functionality is expressed using ordinary C-code. In recent work [7] the -core language has been extended to provide messages (task execution requests with timing offsets):…”