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S7 PLC Buddy

Ladder Migration Overview

The Ladder Migration feature converts most vendor’s Ladder Diagram (LAD) programs to Structured Control Language (SCL) using the AI Agent. It targets engineers who need to modernise legacy Ladder programs — to make them easier to maintain, review in version control, or adapt for new projects.

Why migrate to SCL?

Section titled “Why migrate to SCL?”
  • Readability — SCL reads like code, which is easier to review in diff tools and version control (Git).
  • Tooling — modern code analysis, formatting, and search tools work on text.
  • Portability — SCL blocks can be imported into any S7-1500/1200 project.
  • AI assistance — the AI Agent can explain, review, and extend SCL far more effectively than Ladder.

What the migration does

Section titled “What the migration does”

Given Ladder network diagrams (exported as a PDF):

  1. The AI Agent reads each network’s contact and coil diagram.
  2. It converts the Ladder logic to semantically equivalent SCL.
  3. It adds inline comments explaining what each section does.
  4. It flags any constructs that are ambiguous or require your review.

What it handles well

Section titled “What it handles well”
Construct Support
Normally open / closed contacts Full
Output coils (SET, RESET, output) Full
Comparison instructions Full
Math and arithmetic Full
Timer and counter calls (IEC timers) Full
Move / type conversion instructions Full
Standard FB instance calls (simple parameter sets) Good
Complex nested call structures Partial — review required

Known limitations

Section titled “Known limitations”
  • FB instance calls with many parameters — the agent reconstructs these from the PDF but complex inline call structures may need manual cleanup.
  • Network-level comments — preserved as // comments above each network’s SCL, but formatting may not be perfect.
  • Hardware-specific instructions — instructions that map directly to hardware (e.g. DPRD_DAT) are included but may require adaptation.
  • ENO handling — explicit ENO := TRUE patterns in converted blocks may be simplified.

Requirements

Section titled “Requirements”
  • The Ladder Migration MCP server must be running (connected via Settings → Connections → Ladder Migration MCP).
  • A PDF export of the Ladder program (most vendors have a print/export function).
  • TIA Portal connected (optional, but required if you want the agent to import the result directly).

Next steps

Section titled “Next steps”