Glossary · PLC and control programming
STEP 7 ladder logic (LAD)
Also known as: LAD, KOP
German: KOP (Kontaktplan)
In Siemens STEP 7 and TIA Portal, LAD (German KOP, Kontaktplan) is the name of the ladder diagram programming language, which represents logic as contacts, coils and boxes between power rails.
- PLC programming
- Vendor product
In one sentence
LAD, called KOP in German, is the Siemens name for the ladder diagram language in STEP 7 and TIA Portal.
Example
A Siemens program shows the start/stop circuit of a pump motor in LAD as a normally open start contact, a normally closed stop contact and an output coil.
How it applies
- Engineering: LAD is the Siemens implementation of the IEC 61131-3 Ladder diagram (LD) concept. Its instruction set, box instructions and editor behavior follow Siemens conventions, so code is not directly portable to other vendors' LD editors.
- Maintenance: Siemens-trained technicians often know the language by its German abbreviation KOP, together with FUP for function block diagram and AWL for statement list. Service instructions for international teams should give both abbreviations.
- Migration: When projects move between Siemens controller generations, LAD networks can usually be migrated, but some instructions change; the migration result has to be reviewed and tested.
- Documentation: Manuals written in English and German should use the matching pairs consistently: LAD/KOP, FBD/FUP, STL/AWL, SCL. A terminology entry with both forms avoids confusion in translation.
LAD vs. LD
LD is the language name in IEC 61131-3; LAD is Siemens' name for its ladder language. The idea is the same, the details are vendor-specific.
Keep in mind: product names and features change. Check language names and instruction sets against the vendor's current documentation.