STEP5 Offline Editing: Display Symbols in Ladder Diagrams (V7.23)

STEP5 Offline Editing: Display Symbols in Ladder Diagrams (V7.23)

Siemens STEP5 is the legacy programming environment for the SIMATIC S5 family of PLCs. Engineers maintaining older S5 installations regularly need to open backup archives on a programming PC without a connected CPU, view the program in ladder logic (FUP/LAD), and read the logic using the original symbol names rather than the absolute operand identifiers (I 0.0, F 0.0, etc.). This reference documents the exact project settings, file roles, menu paths, and keyboard shortcuts required to make the symbolic display appear in the offline ladder editor for STEP5 versions 7.02 and 7.23.

Overview of the Offline Symbol Problem

When a STEP5 project is uploaded from the CPU or restored from a backup archive, three text files carry the human-readable information that turns a raw program into a readable document:

• *Z0.INI – the symbol/INI file. This is the binary-ish text file the editor reads to resolve every absolute operand (E0.0, A0.1, M0.0, etc.) to its symbolic name and comment.
• *Z0.SEQ – the assignment list (Zuordnungsliste). It is the editable source of the symbol table and is used to regenerate the INI file when the INI is missing or out of date.
• *Z0.PG / *Z0.PE / *Z0.PB / *Z0.FB / *Z0.OB / *Z0.SB / *Z0.DB – the program section files for each block type (PG = program generator blocks, PE = program end, PB = program blocks, FB = function blocks, OB = organization blocks, SB = step blocks, DB = data blocks). Block files contain the actual instruction list or ladder logic.

STEP5 always opens with the absolute representation by default. The ladder editor only switches to symbolic mode when:

1. A valid symbol file (*Z0.INI) is selected in the project setup, and
2. The Display Symbols flag is enabled in the same dialog, and
3. The block is opened in an editor that supports symbolic display (the FUP/LAD editor on F5/F7, not the raw instruction list view).

If any of these three conditions is missing, the editor will still load the block, but it will show only absolute operands such as E 0.0 instead of -S1_START_BUTTON.

Prerequisites

Step-by-Step: Activating Symbolic Ladder Display

Step 1 – Open the project and launch project setup

Start STEP5 and load the backup:

1. File → Project → Open
2. Browse to the unzipped backup folder and select the *Z0.ST (status/control) or any block file that belongs to the project (e.g. PR0732Z0.ST). STEP5 auto-detects the rest of the file set.
3. Once loaded, go to File → Project → Set (German: Datei → Projekt → Einstellen). The project setup dialog has five tabs in V7.23: General, Blocks, Symbol File, Comments, and Other.

Step 2 – Configure the Symbol File tab

In the project setup dialog, open the Symbol File tab (German: Symbolik, tab 3 in V7.02). Configure the following parameters:

Step 3 – Configure the Blocks tab

Open the Blocks tab and verify the block type filter matches what you intend to edit. The standard selection is:

• PB (Program Blocks) – always enabled for ladder review
• FB (Function Blocks) – enable if the project uses FBs
• OB (Organization Blocks) – enable for cyclic/scan/OB1 review
• SB (Step Blocks) – enable for GRAPH 5 / step sequence projects
• DB (Data Blocks) – leave enabled for data word inspection

Press the Generate button (German: Generieren) at the bottom of the Blocks tab. STEP5 will parse the SEQ and produce the INI file in the project directory. If you see an error popup, check the SEQ file for syntax errors – common causes are missing column delimiters or non-ASCII characters in symbol names.

Step 4 – Open the Assignment List and save

From the main menu, choose Editor → Assignment List (German: Editor → Zuordnungsliste) or press F7. The assignment list opens in a tabular editor with the following columns:

Press F7 again to save. Saving the assignment list triggers the regeneration of the *Z0.INI file in the same directory. A status line at the bottom of the screen reports Z0.INI generated.

Step 5 – Open the Ladder Editor with symbols

Return to the project navigator, select a block (e.g. PB 5 or PB 32), and open it in the FUP/LAD editor. The block should now render with symbolic operands in the contact/coil labels. To toggle between symbolic and absolute view at any time, press Shift-F3 in the editor. This is the most useful diagnostic key: if Shift-F3 toggles correctly but the initial view is absolute, the project setup was not reloaded – close and reopen the block.

Project File Layout and File Roles

The file naming convention for a STEP5 project named PR0732 is:

The * in filenames is a literal placeholder for the project number; STEP5 substitutes the digits at load time. Inspecting the SEQ file with a text editor such as Notepad will reveal the complete symbol/comment table and is a quick way to confirm whether symbols exist in the backup at all.

Menu and Keyboard Reference (V7.23 English)

Differences Between STEP5 V7.02 and V7.23

Both versions store the same file types and use the same INI/SEQ pair, but the menu structure and default dialog labels differ:

Engineers maintaining both versions should treat V7.02 as the more conservative path: open the assignment list with F7, save with F7, and verify the INI timestamp updates before opening any ladder block.

Troubleshooting Matrix

Verification

After configuration, confirm the symbolic display is active using the following checks:

1. Open PB 1 (or any PB that is known to use I/O) in the FUP editor. The contact and coil labels should show --| |-- blocks with symbol text such as -S1_START rather than -E 0.0.
2. Press Shift-F3. The labels should toggle to absolute (-E 0.0) and back. This confirms the editor is reading the INI file.
3. Cross-reference: press Ctrl+F7 and look up E 0.0. The result should list the symbol name in the Symbol column. If the symbol column is empty, the INI is stale – F7 in the assignment list and re-open.
4. Open the assignment list (F7) and confirm the symbol column matches the labels you see in the ladder. Mismatches indicate the wrong project number is loaded.

Reference Documentation

The complete STEP5 user manual, including project setup, editor usage, and offline workflow, is published by Siemens as entry ID 9830806 in the Siemens Industry Online Support portal:

• STEP5 Programming Package – User Manual: https://support.industry.siemens.com/cs/ww/en/view/9830806
• Siemens Industry Online Support – Legacy SIMATIC S5 / STEP5 landing page: https://support.industry.siemens.com/cs/ww/en/view/109751706

Field Notes and Best Practices

• Always back up the *Z0.SEQ file separately from the rest of the project. The SEQ is the only human-readable source of the symbol table; if it is lost, symbols must be reconstructed manually from electrical drawings or the original machine documentation.
• If a backup was taken with a third-party tool that strips the INI, do not attempt to edit the block in FUP view until the INI is regenerated from the SEQ. Editing in absolute-only mode is fast but the next upload to the CPU will overwrite the symbolic information.
• When migrating logic into STEP7 / TIA Portal, export the SEQ to CSV first (manual conversion of column format). The S5 symbol format differs from the S7 symbol table; the standard S5 import in STEP7 V5.x is the S5 to S7 Converter.
• For very old S5-100U and S5-115U programs, the STEP5 version on the engineering PC must be at least as new as the one used to create the program. Newer V7.23 will read V6.x projects, but the reverse is not true.

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