Learn what structured text is, why it is safer, how to use it, what are the challenges, and what are the benefits of using this programming language in PLCs.

El lenguaje de programación de Texto Estructurado (Structured Text o ST) se utiliza comúnmente en el desarrollo de controladores lógicos programables (PLCs). Su estructura aporta varias ventajas que contribuyen a mejorar la seguridad en los PLCs: Legibilidad y Mantenimiento: El ST enfatiza un código claro y estructurado, lo que facilita su lectura y mantenimiento. La legibilidad mejorada reduce la probabilidad de errores durante las modificaciones, mejorando así la seguridad del sistema de control. Modularidad y Reusabilidad:El ST admite la programación modular, permitiendo la división del código en funciones o bloques reutilizables.

How can structured text programming language improve safety in PLCs?

Programmable logic controllers (PLCs) are widely used in industrial automation and control systems. They can perform complex tasks, such as monitoring sensors, controlling actuators, and implementing logic and arithmetic operations. However, they also pose safety risks if they malfunction, are misconfigured, or are hacked. Therefore, choosing the right programming language for PLCs is crucial to ensure reliability, efficiency, and security. In this article, we will explore how structured text (ST), one of the five standard languages for PLCs, can improve safety in PLCs.

1 What is structured text?

Structured text is a high-level, text-based programming language that resembles Pascal or C. It allows programmers to write code in a more readable and flexible way than ladder logic (LL) or instruction list (IL), which are graphical and low-level languages. ST can use variables, data types, functions, loops, conditional statements, and other common programming elements. It can also interact with other languages and devices through communication protocols and interfaces.

Add your perspective

Ing.Jhonatan Lizcano 📝Socio tecnológico

⚡️Automatización industrial , ejecución de proyectos y tecnología
Report contribution
El lenguaje de programación de Texto Estructurado (Structured Text o ST) se utiliza comúnmente en el desarrollo de controladores lógicos programables (PLCs). Su estructura aporta varias ventajas que contribuyen a mejorar la seguridad en los PLCs: Legibilidad y Mantenimiento: El ST enfatiza un código claro y estructurado, lo que facilita su lectura y mantenimiento. La legibilidad mejorada reduce la probabilidad de errores durante las modificaciones, mejorando así la seguridad del sistema de control. Modularidad y Reusabilidad:El ST admite la programación modular, permitiendo la división del código en funciones o bloques reutilizables.

Translated

Like
Ravi Sharma

Robotics | Automation | Robots | PLC | HMI | ROS | Python | C, C++, C# | Simulation | Industry 5.0
Report contribution
Structured Text is a syntax-based language that is similar to other programming languages such as C++, and Python. For instance, Siemens PLCs can be programmed using Structured Text (SCL), which is inspired by Pascal. Programs written in ST are compact, easy to understand, and reusable. They significantly reduce the number of lines required to write an application. Structured Text has all the features available to any other programming language, such as Ladder and FBD, to program a PLC. It can access IOs, variables, and tags, and allows writing efficient comments, thus increasing the code readability manifold. I prefer to write PLC code in Structured Text unless there is a specific requirement to write the code in other languages.🙂👍

Like

2 Why is structured text safer?

Structured text can improve safety in PLCs for several reasons. First, it can reduce human errors and bugs by using descriptive names, comments, and modular code. This makes the code easier to understand, maintain, and debug. Second, it can enhance performance and efficiency by optimizing memory usage, execution speed, and resource allocation. This reduces the chances of overloading, overheating, or crashing the PLC. Third, it can increase security and protection by using encryption, authentication, and error handling. This prevents unauthorized access, tampering, or corruption of the PLC code and data.

Add your perspective

3 How to use structured text?

To use structured text in PLCs, programmers need to follow some basic steps. First, they need to select a suitable development environment and a compatible PLC. There are various software tools and hardware platforms that support ST, such as CODESYS, Siemens TIA Portal, or Allen-Bradley Studio 5000. Second, they need to define the inputs and outputs of the PLC, such as sensors, switches, valves, or motors. These can be assigned to different memory locations and data types in the ST code. Third, they need to write the ST code using the syntax and rules of the language. They can use predefined or custom functions, libraries, and data blocks to structure the code. Fourth, they need to compile, download, and run the ST code on the PLC. They can also test, monitor, and modify the code using simulation, debugging, or online editing tools.

Add your perspective

4 What are the challenges of structured text?

Structured text can be challenging to use. Programmers may need to learn new concepts, commands, and conventions to use ST effectively, as it requires more programming skills and knowledge than LL or IL. Additionally, ST may not be compatible with some older or proprietary PLCs, so adapters, converters, or other languages may be necessary for communication. Furthermore, ST can introduce more complexity and abstraction to the PLC code, requiring more attention to the logic, data, and flow of the code for error-free operation.

Add your perspective

5 What are the benefits of structured text?

Structured text offers many benefits for PLC programmers and users, despite the challenges. Productivity can be improved by allowing programmers to write code faster, easier, and more flexibly, as well as having the ability to reuse, modify, and share code more conveniently. Additionally, structured text can improve quality and reliability by reducing errors, bugs, and failures. It can also enable more advanced and sophisticated features and functions for the PLC. Moreover, structured text can improve safety and security by enhancing performance, efficiency, and protection. It is also beneficial in helping to comply with industry standards and regulations for PLC programming.

Add your perspective

Rareș Curatu

Driving the Development of Industry 4.0 and Innovation in the Global Industrial Automation and Machinery Business
Report contribution
ST is more expressive and flexible, so it can be used to implement more complex algorithms easier and more efficiently. I also find it more reusable than the other IEC61131-11 languages. ST can also be easier to read when you have more code. A significant improvement over long IL programs or FBD spaghetti code.

Like

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

Add your perspective

How can structured text programming language improve safety in PLCs?

1

2

3

4

5

6

1 What is structured text?

2 Why is structured text safer?

3 How to use structured text?

4 What are the challenges of structured text?

5 What are the benefits of structured text?

6 Here’s what else to consider

Control Engineering

Rate this article

Thanks for your feedback

More articles on Control Engineering

More relevant reading