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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 info@emea.com.tr


IEC 61131-3 controllers converted from any kind of intelligent device – by means of the adaptable CODESYS Control runtime system.

EMEA Technology

Runtime Toolkit

SDK for the implementation of industrial IEC 61131-3 controllers with a customized PLC runtime system programmable with CODESYS

EMEA Technology


CODESYS Control is the corresponding runtime system to the CODESYS Development System.

EMEA Technology

CODESYS Virtual Control SL

The IEC 61131-3-compatible runtime system CODESYS Virtual Control SL can be installed on any architecture with container or hypervisor / VM - as often as required and with scalable performance.

EMEA Technology


Compact software interface (API) for easy access to the PLC variables in CODESYS controllers from external systems

EMEA Technology

OPC Server

Standard Interface to access the IEC 61131-3 process data of a controller via Open Platform Communications.

EMEA Technology


Standard Interface for Communication in Smart Factory and Industry 4.0 Systems

EMEA Technology


Add-on component for standard devices with Symmetric Multicore Processing (SMP) support

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