Managing Siemens Micro Memory Cards (MMC) requires specific procedures because these are not standard flash drives. While they may physically resemble standard SD cards, they use a proprietary formatting system essential for SIMATIC S7-300 Go to product viewer dialog for this item. Go to product viewer dialog for this item. controllers. The Golden Rule: Never Format in Windows
Standard operating system formatting (FAT32, NTFS) will permanently damage a Siemens MMC, making it unusable in a PLC environment. A standard PC card reader can often read the data, but attempting to "Format" via Windows Explorer destroys the hidden system image Siemens uses to identify the card to the CPU. Authorized Methods to Format or Reset a Siemens MMC
Instead of a third-party "format tool," use the following built-in methods provided by Siemens software and hardware: 1. Hardware Reset via CPU ( Go to product viewer dialog for this item.
This is the most common way to clear a card when you don't have a PG/PC connection: Insert the MMC into the S7-300 CPU Go to product viewer dialog for this item. slot.
Hold the switch to the MRES position for roughly 9 seconds until the STOP LED lights up continuously.
Release the switch and immediately (within 3 seconds) flip it back to MRES.
The STOP LED will blink while the MMC is being "reset" to its factory-delivered state. 2. TIA Portal "Format Memory Card" ( Go to product viewer dialog for this item. siemens mmc card format tool
For newer controllers, the TIA Portal Engineering Software provides a dedicated tool: Go to Online & Diagnostics for the connected CPU. Expand the Functions folder in the project tree. Select Format memory card and click the Format button.
Confirm the prompt. Note: The CPU must be in STOP mode to complete this action. 3. SIMATIC Manager "Delete Blocks" (
If you want to clear the program but keep the card's integrity: siemens mmc card - Support
Siemens SIMATIC Micro Memory Card (MMC) is a cornerstone of industrial automation, specifically for Siemens S7-300 and S7-400 PLC series
. While it shares a physical form factor with standard consumer memory cards, its underlying architecture and file system are proprietary. Understanding how to properly "format"—or more accurately, reset—these cards is critical for maintaining system integrity and avoiding permanent hardware damage. The Purpose of the Siemens MMC
The MMC acts as the non-volatile load memory for the PLC, storing the user program, hardware configuration, and retentive data. Unlike newer S7-1200 or S7-1500 models that have internal memory, S7-300 CPUs typically cannot run without an MMC inserted The Perils of Standard Formatting Managing Siemens Micro Memory Cards (MMC) requires specific
One of the most common mistakes in industrial maintenance is attempting to format a Siemens MMC using a standard Windows formatting tool or digital camera. Irreversible Damage
: Standard PC formatting overwrites the proprietary Siemens file system. Once formatted as a standard FAT or NTFS drive, the card may become unusable for the S7-CPU Hardware Rejection
: The PLC validates the card's internal CID (Card Identification) and CSD (Card Specific Data) registers. If these registers do not match the expected Siemens signatures, the CPU will report a "Memory Card Invalid" Authorized Formatting and Reset Methods MMC card - SiePortal - Siemens
And MMC is here a Micro Memory Card which has the same dimensions as a SD card. An MMC should allways be an original Siemens part. sieportal.siemens.com
It looks like you're looking for the Siemens MMC Card Format Tool—a specific utility used primarily for Siemens industrial automation systems (e.g., Simatic S7, C7, WinAC).
Important distinction:
This tool is not for standard MMC cards used in cameras or phones.
It's for Siemens-format MMC cards (often 4 MB, 8 MB, 64 MB, 128 MB) used as load memory for PLCs. 🔁 Summary Table
| Action | Tool | Works
| Action | Tool | Works? | |--------|------|--------| | Windows right-click format | Windows Explorer | ❌ Destroys card | | SD Association Formatter | SD Formatter | ❌ Destroys card | | DiskPart / disk utility | CMD | ❌ Destroys card | | Siemens SIMATIC MMC Formatter | Siemens tool | ✅ Correct | | SIMATIC Manager > PLC > Format MMC | STEP 7 + Prommer | ✅ Correct |
The tool will show a drop-down menu of removable drives. Do not guess. Look for the drive letter that corresponds exactly to your prommer (e.g., "Removable Disk (F:)"). Critical: If your PC has multiple removable drives (SD card slots, phone drives), unplug them to avoid accidental formatting.
In Simatic Manager, you can set the card properties. For deployed machines, it is often wise to leave the card as "EPROM" transfer or use the "Know-How Protection" in the blocks to prevent unauthorized tampering, which reduces the need for formatting due to user error.
Before we open the software, it is vital to understand the hardware. Siemens Memory Cards (MMC) and Micro Memory Cards are Flash EPROMs.
Unlike a standard USB stick which uses generic mass storage drivers, Siemens MMCs contain internal controllers and firmware designed to interact specifically with the S7 CPU. They hold the user program, the hardware configuration, and data blocks.
Because of this specialized nature, Windows cannot natively format these cards correctly. If you try to format an S7 MMC using Windows Explorer (FAT32/NTFS), you will likely strip the card of its boot sector and Siemens-specific file system, effectively rendering it useless for a PLC until it is repaired.
Therefore, you must use tools designed by Siemens to handle the low-level formatting and file system reconstruction.