When the CPU’s STOP LED flashes slowly (approximately 0.5 Hz), it indicates a memory inconsistency and requests a format. Here is the procedure:
To use this method, your PC must be equipped with a specialized Siemens field PG (Programming Device) or an external USB Prommer (such as the Siemens SITOP/SIMATIC USB Prommer). Standard USB card readers will not work with official Siemens software.
Within 3 seconds, press and hold the switch back down to the position again. siemens mmc card format tool
Siemens provides several official (and safest) methods for handling MMC cards. These should always be your first choice.
A standard PC card reader (older internal card readers connected via USB/PCI often work best). When the CPU’s STOP LED flashes slowly (approximately 0
For the latest updates, search Siemens Support Entry ID: 27008420 or contact your local Siemens automation partner.
Right-click and select , or select Clear/Reset from the PLC menu. Note: This clears user programs safely without touching the critical system geometry. Method B: Card Reset via the PLC CPU Within 3 seconds, press and hold the switch
Do not attempt to "fix" it using Windows Disk Management.
: A lightweight, freeware tool designed to read and write low-level sector images of Siemens S7 MMCs.
Older multi-in-1 USB 2.0 card readers that explicitly list "MMC" support (not just SD/MMC combo support) are often required. Modern USB 3.0/4.0 card readers usually fail to communicate with Siemens cards at a raw register level.