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When modelling, you connect sequence logic and assemblies in a bit-controlled manner. The function of the sequence uniquely describes each state.



From this model, an algorithm generates the error-free PLC code (PLC Open XML) and the HMI - without any further manual programming.



SELMOstudio is currently focussing on the Beckhoff TwinCAT 3 system; the runnability for CODESYS is about to break through. Other platforms will follow.


Create your PLC program faster and easier - Sequences and Structures based on SELMO

With the Modeller function, you can create sequences (state machines) and digitally document your machine system. This requires a change in thinking from transition-based sequence programming to discrete state modelling. This initial effort pays off quickly:

The integrated generator creates the sequence-logic software and the user interface automatically. With SELMO, you can process and display every possible bit pattern of a state machine. 

Technical advantages with SELMO


Process and machine sequences in graphical form usually serve as the basis for programming the sequence. The description is doubly complex: First graphically-informally, to create a common understanding of the process, and then formally in PLC code for implementation. SELMOstudio creates PLC and HMI code directly from the process description. Only sensors and actuators have to be assigned to the individual steps in the grid layer. As a result, the process engineer-programmer interface disappears completely; the duplication of effort is eliminated

Unit and integration tests are conventionally performed to check software for errors. Standard syntax checks detect many manually caused "typos". Logical or syntactically correct typos, however, have to be searched for by unit tests at great expense. In order to find any deviations from the graphically described sequence, they have to be restarted after each software change. SELMOstudio takes over this translation work for the programmer and generates syntactically correct, error-free software. As with any other programming or modelling method, the process steps must be correctly formulated in advance.

SELMOstudio generates not only the PLC code from the model, but also the HMI. Inputs and outputs are modelled as zones. Programmers can define which zones require an HMI button for operation. The modelled sequence with all steps and zones is generated directly and the diagnosis is derived from it. The operator receives a consistent, plant-independent operating concept. For maintenance, there is no longer a system standstill without an error message. Each step chain reports the error and indicates what is missing in order to continue. In this way, SELMOstudio minimises downtimes and maximises plant availability. In the most recent SELMO retrofit project, for example, throughput was increased to over 25 percent.

To make the software maintainable, large plant operators specify software standards or structures. These specifications have to be elaborately implemented by system integrators and consistently adhered to. After all, acceptance is the goal. PLC code generation with SELMOstudio, on the other hand, automates compliance with the standard: The code always has the same structure, regardless of function. The SELMO standard makes the code easy to understand because it is always structured in the same way - whether for a single machine or an complete assembly line.

Every internationally supplying machine manufacturer or system integrator knows the problem: the same plant has to be delivered with different control systems for different target markets. For the plant operator, it makes sense to prescribe the control system to the supplier in order to avoid the complexity of different hardware in the factory. The reverse conclusion, however, is that the software must be rewritten or manually adapted for each required control system. SELMOstudio, on the other hand, generates the PLC code in accordance with IEC 61131-3, so programmers can import the code into any type of control that complies with this international standard. The software adaptation costs are eliminated entirely.

Common, modern system modelling sometimes comes up against limits because production systems are becoming more and more complex. Many interfaces offer many potential sources of error. The SELMO method is different: it starts directly with the requirements description. The process is the focus, serves as a common view of the system and is simultaneously the model from which the plant software is generated. Because interfaces are eliminated, engineering time is significantly reduced and the scope for interpretation is minimised. SELMO thus leads to an immense increase in efficiency and quality.

SELMO develops many generators for different PLC hardware

Beckhoff - TwinCAT 3

  • PLCOpen XML import
  • PLC Simulation on Windows 
  • Windows based realtime
  • HMI WinForms based


  • PLCOpen XML import
  • PLC Simulation on Windows 
  • Windows based realtime
  • OPC UA Server
  • HMI WinForms based