Glossary · PLC and control programming
Structured Control Language (SCL)
Also known as: SCL, S7-SCL
German: SCL (Structured Control Language)
In Siemens STEP 7 and TIA Portal, Structured Control Language (SCL) is the high-level, Pascal-like textual programming language that corresponds to Structured Text (ST) of IEC 61131-3, with Siemens-specific extensions.
- PLC programming
- Vendor product
In one sentence
SCL is Siemens' Pascal-like text language for PLCs, its implementation of IEC 61131-3 Structured Text with vendor extensions.
Example
The scaling and filter calculations of a Siemens weighing application are written in SCL, while the interlocks remain in LAD.
How it applies
- Engineering: SCL suits calculations, loops, string and data handling and complex state machines. Siemens instructions and system functions are called in SCL syntax, and Siemens-specific data access (for example to data blocks) differs from other ST dialects.
- Migration: SCL is a common target when replacing older statement list (STL/AWL) code. Rewritten code must be tested as new software.
- Portability: SCL code can often be moved to other ST environments with moderate effort, but vendor-specific instructions, addressing and data types need adaptation.
- Documentation: Terminology differs between teams: some say SCL, others ST. In multilingual documentation, use SCL for Siemens tools and ST for the standard language, and explain the relationship once in the glossary.
SCL vs. ST
Structured text (ST) is the language defined in IEC 61131-3. SCL is Siemens' implementation of it, historically a separate product and now integrated into the TIA Portal.
Keep in mind: product names and features change. Check the language scope and supported instructions against the vendor's current documentation.