Siemens S7-300 / S7-400 Ladder Logic (LAD) Programming Manual

About this manual

The manual provides instructions for working with the Ladder Editor, a full language description, and reference material for Ladder Logic (LAD) on Siemens S7-300 and S7-400 programmable controllers. It is aimed at S7 programmers, operators, and maintenance/service personnel and assumes a working knowledge of automation procedures.

The document is organized into two main parts: Part 1 covers the use of the Ladder Editor, creation of logic blocks, data blocks, and program testing; Part 2 describes the language elements, addressing, bit‑logic, timer, counter, and arithmetic instructions. Appendices include a glossary, index, and reference lists for related Siemens manuals.

What's inside

• Working with the Ladder Editor
• Language Description
• Creating Logic Blocks
• Creating Data Blocks and User‑Defined Data Types
• Editing Block Properties and Testing the Program
• Configuration and Elements of Ladder Logic
• Addressing
• Bit Logic Instructions
• Timer Instructions
• Counter Instructions

Frequently asked questions

Who is the intended audience for this manual?

The manual is intended for S7 programmers, operators, and maintenance/service personnel.

Which version of STEP 7 software does this manual apply to?

It is valid for release 3.0 of the STEP 7 programming software package.

How can I get technical assistance for the content of this manual?

You can contact a Siemens representative or call the hotline at (+49) (911) 895‑7000.