Should I Switch from Ladder Logic to SCL in TIA Portal Programming?

I concur with Jesper's sentiments. I once faced a challenging situation where the lead engineer insisted on utilizing ST (SCL), which led to various issues that resulted in prolonged coding and debugging processes. The on-site engineers were dissatisfied, and my reputation suffered, despite my explanation that it was at the behest of the chief engineer. It was a classic case of someone who wanted to appear knowledgeable and boastful. This individual constantly showcased his latest iPhone and its capabilities, to which I would casually mention that my phone also had similar features at a fraction of the cost. I'm sure many have encountered such individuals in their professional circles.

• 07-08-2024
• parky

Parky and Jesper both made valid points that resonate with my own experiences. I once encountered a situation where the chief engineer insisted on using ST (SCL), which led to numerous coding and debugging issues, ultimately causing delays. This is why I prefer to limit my use of SCL/STL. While I may not be an expert, I understand the importance of maintaining code in a clear and understandable format for future reference. As Jesper mentioned, LAD programming with a 1200 or 1500 PLC offers ample flexibility and functionality.

• 08-08-2024
• Puddle

During the S5 era, I primarily used STL for my coding as it was the only option for writing Function Blocks (FBs) at the time. I found STL easier to work with compared to ST (SCL) because it was quicker to input, although it could be challenging for other engineers to grasp. While I often implemented output handling in ladder program blocks, the control logic was mostly written in STL within the FBs (there were no Function Calls (FCs) back then). Despite the inconvenience of numerous brackets, which were more easily managed in ladder logic, I became proficient in STL and didn't find it problematic. I recall exclusively writing my program blocks in STL, ensuring proper bracketing and segment end commands to facilitate translation into ladder logic for faster execution. Unfortunately, FBs couldn't be visualized in ladder logic. I have a vivid memory of someone requesting me to convert a program originally written for an S5 110, utilizing a PG675 handheld programmer. The program lacked segment end instructions, rendering it impossible to display in ladder logic. After meticulously adding the necessary segment end instructions (**** or BLD255), I successfully translated the program into ladder logic, downloaded it to the PLC, and seamlessly transitioned it to ladder logic programming.

• 09-08-2024
• parky

For nearly two decades, I have been proficient in programming Siemens systems. Throughout my experience, I have found that utilizing ladder logic and Function Block Diagrams (FBD) is essential. While familiarity with Structured Text (STL) and Statement List (SCL) can be beneficial, my preference is to primarily focus on ladder and FBD due to their efficiency. However, there have been occasions where knowledge of STL and SCL has been necessary, particularly when working with older codes or utilizing indirect addressing on the 300/400 platform.

• 09-08-2024
• Lare

It is worth mentioning that TIA in ladder programming also allows for indirect addressing.

• 09-08-2024
• Rob...

Back in the day, S5 FB's were exclusively programmed in STL, which is where I gained my initial experience in the early 80's. I continued to use it until 2000 and found it to be quite enjoyable. However, with advancements in technology, the necessity for STL has diminished as many functions that were previously limited to STL can now be accomplished in LAD/FBD, or whatever you prefer to call it. Despite its benefits for complex calculations, I personally do not favor ST for normal Bool code. It's worth noting that ST and STL are two distinct programming languages - ST is a structured language similar to Pascal while STL is more like assembler. Although STL code can be easily translated into ladder logic, ST code poses a greater challenge due to its supposed portability. Many PLC functions are custom-made for specific platforms, making it difficult to seamlessly transfer ST code to different systems without extensive modification. For instance, a simple code like INT_To_Str in one PLC may need to be adjusted to Int_To_STR in another platform due to differences in letter casing. Additionally, naming conventions vary across platforms - a tag like Stop_Drive may be acceptable in one system but could cause compilation errors in another where "Stop" is a reserved keyword.

• 09-08-2024
• parky