Works with standard PC hardware; bypasses Windows file system restrictions.
Click . Once complete, the hidden Siemens structure is restored, and the card can be inserted back into a PLC or Step 7. 2. Win32 Disk Imager or BalenaEtcher
💡 If the tool cannot read the card at all, try a different card reader. Some modern generic USB readers struggle with the proprietary format of Siemens industrial cards.
Here are a few options for a post about the , tailored for different platforms (LinkedIn/Professional vs. Technical Forum/Blog).
Insert the Siemens MMC into the PG card slot or USB Prommer. Open or STEP 7 Manager .
The S7 PLC will reject the card, showing a flashing SF (System Fault) or BF (Bus Fault) LED. The PLC will no longer boot or accept hardware configurations. Top Tools for Formatting and Managing Siemens MMCs 1. Siemens STEP 7 / TIA Portal (The Official Method) siemens mmc card format tool
Siemens technically distinguishes between "formatting" and "resetting." You can perform these actions safely only through Siemens hardware or software: : Insert the card into the CPU.
Standard formatting deletes the Siemens-specific Layer 4 system files and blocks.
Industrial automation engineers worldwide have long wrestled with a silent but costly threat: the accidental destruction of a Siemens SIMATIC MMC (Micro Memory Card). A single inadvertent click in Microsoft Windows can transform a critical piece of automation hardware into electronic waste.
A standard MMC and a Siemens MMC look identical, but Windows sees a Siemens card as "unformatted" or "raw" because it cannot read the proprietary boot loader and project data sectors. If you click "Format" in Windows, you the internal header that the PLC needs to recognize the card. 2. The Tool: Restoration and "Reset"
Use the function to save a backup image of a working MMC. Works with standard PC hardware; bypasses Windows file
, which clears all user data while preserving the system structure.
Use the function to restore a clean, working Siemens .img file onto a corrupted card.
The safest and most official way to clear a Siemens MMC is using the programming software itself. This method preserves the card's internal operating structure while clearing user program data. Requirements:
The Ultimate Guide to Siemens MMC Card Format Tools: How to Format and Recover S7 Micro Memory Cards
Alternatives
A slow, rhythmic blinking (0.5 Hz) of the STOP LED usually indicates that the CPU is requesting a memory reset (MRES) or that the inserted MMC is unformatted/corrupted. Hold the MRES switch down for 9 seconds until the light stays solid, release it, and quickly press it down again for 3 seconds to trigger an internal format.
Comprehensive Guide to the Siemens MMC Card Format Tool: Resetting and Troubleshooting S7-300 Memory Cards
Insert the MMC into a standard multi-card reader (Note: some modern USB 3.0 readers block raw commands; older internal or USB 2.0 readers often work best). Run the tool as an Administrator.
Standard operating systems (Windows, macOS, Linux) do not recognize the internal structure of a Siemens MMC.