IT OT Convergence

CODESYS

6 min read

CODESYS

CODESYS is a vendor-neutral software platform for Industrial Automation, used to develop, configure and run PLC programs on Soft PLCs, industrial controllers, Embedded systems and edge platforms. The platform supports the IEC 61131-3 programming languages and is one of the most widely used ecosystems worldwide for software-based industrial control.

CODESYS is deployed within Industrial Automation, SCADA, machine building, Building Automation, energy infrastructures and Industrial Internet of Things environments. The platform plays an important role in the shift from hardware-based PLCs to software-defined automation and IT OT Convergence.

In modern OT architectures, CODESYS combines classic PLC functionality with Motion Control, fieldbus integration, visualisation, Edge Computing and industrial communication protocols such as OPC UA, MQTT, EtherCAT and ProfiNET.

⚙️ What is CODESYS

CODESYS stands for:

Controller Development System

The platform was originally developed by the German company 3S-Smart Software Solutions and grew into a de-facto standard for IEC 61131-3 engineering environments.

CODESYS consists of:

Component Function
CODESYS Development System Engineering environment
CODESYS Runtime PLC runtime
CODESYS Control Soft PLC engine
CODESYS Visualization HMI functionality
CODESYS Motion Motion control
CODESYS Safety Safety functionality
CODESYS Fieldbus Stack Industrial communication
CODESYS Edge Edge computing integration

The platform runs on diverse hardware:

  • industrial PCs
  • embedded ARM systems
  • Linux platforms
  • Windows systems
  • hypervisors
  • edge gateways
  • industrial controllers

🏗️ Architecture of CODESYS

CODESYS uses a modular architecture in which engineering, runtime and communication are logically separated.

Typical architecture:

Engineering Workstation
        │
        ▼
    CODESYS IDE
        │
        ▼
Communication Layer
        │
        ▼
 CODESYS Runtime
        │
 ┌──────┼──────┐
 ▼      ▼      ▼
IO   Fieldbus  Motion

The runtime handles:

  • cyclic tasks
  • Real-time scheduling
  • IO updates
  • protocol handling
  • motion control
  • diagnostics
  • visualisation

Within a Soft PLC architecture, the runtime functions as a software-based PLC.

💻 IEC 61131-3 programming languages

CODESYS supports all standard IEC 61131-3 languages:

Programming language Application
Ladder Diagram (LD) Electrical logic
Function Block Diagram (FBD) Process logic
Structured Text (ST) Complex algorithms
Sequential Function Chart (SFC) Sequential processes
Instruction List (IL) Legacy systems

Structured Text is increasingly dominant within modern automation because of:

  • better scalability
  • reusability
  • object-oriented capabilities
  • complex logic
  • data handling

Especially within motion control and IIoT projects, ST is widely used.

🧠 Runtime and real-time behaviour

The CODESYS Runtime executes PLC logic cyclically.

Important runtime components:

Component Function
Task Scheduler Cyclic execution
Memory Manager Memory management
IO Handler Field equipment
Protocol Stack Industrial communication
Watchdog Monitoring
Debug Engine Online diagnostics

Real-time behaviour depends strongly on:

  • host operating system
  • CPU priorities
  • Hypervisor configuration
  • network load
  • the fieldbus used

For deterministic control, the following are often used:

  • real-time Linux
  • dedicated CPU cores
  • TSN
  • real-time Ethernet
  • hardware timestamping

🔌 Industrial communication

CODESYS supports a wide range of industrial protocols.

Ethernet-based protocols

Serial protocols

Building automation

Energy infrastructures

This allows CODESYS to function as an integration platform between diverse OT systems.

⚡ Motion control

CODESYS includes extensive motion control functionality.

Supported functions:

  • positioning
  • camming
  • gearing
  • interpolation
  • servo control
  • multi-axis synchronisation

Applications:

  • packaging machines
  • Robotics
  • CNC machines
  • AGV systems
  • conveyor systems

For motion control, protocols such as the following are typically used:

Real-time performance is essential here because of low tolerances for Jitter and Latency.

🖥️ Visualisation and HMI

CODESYS includes integrated visualisation functionality.

Capabilities:

  • web visualisation
  • HTML5 HMI
  • dashboards
  • alarms
  • Trending
  • user management
  • remote operation

This allows simple HMI and SCADA functionality to be integrated directly within the PLC environment.

Benefits:

  • less external software
  • fast engineering
  • integrated data flow
  • central configuration

Drawbacks:

  • higher runtime load
  • larger attack surface
  • limited scalability for large installations

☁️ Edge Computing and IIoT

CODESYS is increasingly used within Edge Computing architectures.

Functionalities:

  • protocol conversion
  • local analytics
  • MQTT publishing
  • OPC UA server
  • cloud connectivity
  • data buffering

Typical integrations:

Platform Use
Azure IoT Cloud analytics
AWS IoT Monitoring
Unified Namespace Data integration
Historian Time-series storage
MES Production data

This creates a hybrid OT/IT architecture.

🔒 Cybersecurity within CODESYS

Because CODESYS runs on standard operating systems, cybersecurity measures are crucial.

Risks

Important threats:

  • Malware
  • Ransomware
  • credential theft
  • remote code execution
  • supply-chain attacks
  • unauthorised engineering access
  • manipulation of PLC logic

Attack surface

CODESYS systems often contain:

  • web servers
  • remote engineering
  • network services
  • APIs
  • OPC UA endpoints
  • update mechanisms

Mitigating Measures

Measure Goal
Network Segmentation Zone isolation
Industrial Firewall Protocol filtering
MFA Strong authentication
RBAC Permission management
Application Whitelisting Block unwanted software
Logging Detection
Security Monitoring Monitoring
Patch Management Limit vulnerabilities

In addition, IEC 62443 plays an important role within secure development and OT Hardening.

🏭 Practical applications

Machine building

CODESYS is widely used by OEMs because of:

  • hardware independence
  • fast engineering
  • motion control
  • multi-vendor support

Process industry

Applications:

Often coupled with:

Building automation

Within smart buildings:

Integrations via:

Water and energy sector

Applications:

  • remote Telemetry
  • pumping stations
  • substation automation
  • load management

🧩 Virtualisation of CODESYS

CODESYS runtimes CAN be virtualised.

Supported platforms:

  • VMware
  • Hyper-V
  • KVM
  • Docker containers

Benefits:

  • easy provisioning
  • snapshots
  • central deployment
  • scalability
  • fast Recovery

Risks:

  • real-time degradation
  • hypervisor Latency
  • shared resources
  • storage bottlenecks

For critical real-time applications, dedicated hardware often remains necessary.

⚠️ Operational considerations

Typical failure modes

Issue Impact
Runtime crash Production stop
Memory leak Performance loss
Network congestion Timing issues
CPU overload Jitter
IO timeout Loss of process control
Hypervisor failure Multiple systems offline

Engineering risks

  • incorrect task priorities
  • blocking code
  • insufficient watchdogs
  • incorrect synchronisation
  • race conditions
  • poor exception handling

🔄 Lifecycle Management

CODESYS supports modern software development processes.

Important components:

  • online change
  • versioning
  • library management
  • CI/CD integration
  • remote updates
  • central deployment

Integration with:

This shifts industrial automation increasingly towards software-defined engineering.

🛡️ Safety and Redundancy

For safety-critical environments, CODESYS supports:

Relevant standards:

Within safety-critical processes, validation and certification are essential.

📈 Trends and developments

Important developments:

  • software-defined automation
  • virtual PLCs
  • containerised OT
  • edge-native control
  • integrated AI
  • cloud engineering
  • TSN networks
  • OPC UA PubSub

CODESYS plays a central role in the convergence of:

🎯 Conclusion

CODESYS has grown into one of the most important platforms for modern software-based industrial automation. By combining IEC 61131-3 engineering, Soft PLC functionality, motion control, visualisation and industrial communication, it forms a flexible foundation for modern OT architectures.

The platform supports the shift towards virtualisation, edge computing and software-defined automation, but also brings new challenges around real-time performance, cybersecurity and lifecycle management.

Within modern IT OT Convergence environments, CODESYS provides a powerful bridge between classic industrial control and modern IT-based automation platforms.

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