CODESYS Redundancy Toolkit

Two Industrial IEC 61131-3 Controllers for one Single Application make the Application Fail Safe

CODESYS Redundancy – Fail Safe Controller Applications Developed with the IEC 61131-3 System CODESYS

With the redundancy extension for the IEC 61131-3 programming system CODESYS Development System you can develop redundant controller systems. Two independent industrial controllers simultaneously execute one and the same IEC 61131-3 application while constantly controlling and synchronizing each other. In case of a failure, the passive controller automatically turns into the active controller and operation is continued without interruption. Only the active controller communicates with the I/O system.


  • Library functions for the IEC 61131-3 programming environment CODESYS Development System
  • Plug-in components for the CODESYS Development System for configuring the redundancy functionality
  • Additional component for CODESYS Control
  • Support of I/O systems such as EtherCAT®, CANopen® and proprietary I/O systems
  • Development support for the implementation of CODESYS Redundancy


Requirements for Redundant CODESYS Controllers

  • Access to the CODESYS Control Runtime System implementation required (This means, device manufacturers can only realize CODESYS Redundancy with their own automation devices.)
  • Possible fieldbuses
    • EtherCAT with an integrated CODESYS EtherCAT solution
    • Proprietary I/O systems via an interface for proprietary I/O drivers
  • Direct connecting interfaces between the two controllers

Functional Overview

  • Tested boot-up mechanism for both controllers
  • Configuration of the IP addresses and the timeouts of the controllers
  • Automatic synchronization and update of the redundant controllers with implicitly called CODESYS library functions – even if one of the controllers is replaced by another controller
  • Reaction to errors in the IEC 61131-3 application program
  • Switch between the controllers via function calls from the IEC application or from the device manufacturer runtime system component (for example when monitoring the temperature of a process, upon a fieldbus diagnosis errors or for manual switching via the visualization etc.)
  • Recording of relevant events
  • Synchronization of debugging information, like for example forced variables on both controllers
  • Automatic registration of memory areas to be used by both controllers
  • Private memory areas for each controller, for example for diagnosing the local bus connection
  • Time synchronization of the IEC timers (TIME, TON, TOF,…)
  • Rules for the implementation of redundant controller applications available


  • You are a system integrator or a user in the machine/plant construction sector or the like:
    All you have to do is use a controller already equipped with CODESYS Redundancy.
  • You are a manufacturer of programmable devices:
    Buy the CODESYS Redundancy Runtime Toolkit and implement your own redundant IEC 61131-3 controller.
  • For more information or an offer please contact our sales department under

Overview and Screenshots

CODESYS brochures and information material

CODESYS - One software. All applications. Your Automation Solution.
Version: 10/2023
pdf 2 MB
CODESYS - One software. Any field of application. Your automation platform.
Version: 10/2023
pdf 2 MB
Various suppliers present CODESYS-compatible devices and exciting solutions that can be useful for your automation tasks. (Only available in german language.)
Version: 11/2022
pdf 3 MB