Differences Between Siemens Dedicated Memory Cards and Ordinary SD Cards – All You Need to Know

Differences Between Siemens Dedicated Memory Cards and Ordinary SD Cards – All You Need to Know

All SIMATIC S7 series PLCs are equipped with dedicated memory cards, and the card types vary by model: MMC cards for the S7-300 series, MC RAM and MC Flash cards for the S7-400, SMC cards for the S7-1200/1500 series, and Micro-SD cards for S7-200 SMART. Each memory card has unique functional features, and they are indispensable for some CPU models. This article describes the characteristics of memory cards for S7 series PLCs.

1. SIMATIC MMC Card

MMC stands for Micro Memory Card. It is an EPROM card with power-off data retention capability.

Within S7-300 series PLCs, the MMC card serves as the load memory. Since the CPU modules of the new S7-300 series do not come with built-in load memory, the MMC card is a mandatory accessory for operation.

2. SMC Card

The SMC card shares a similar appearance with standard SD cards and can be read and written via a regular SD card reader. However, strict operational rules must be followed: hidden files on the card must not be deleted, and the SMC card must never be formatted manually. Once formatted, the SMC card will be converted into an ordinary SD card and lose all its dedicated industrial functions. Standard commercial SD cards cannot replace the dedicated memory card for S7-1500 CPUs.

Formatting of SMC cards can only be performed online through TIA Portal. Siemens has not released a dedicated card reader for SMC cards, and regular readers fully meet daily usage requirements.

3. MicroSD Card for S7-1200

The MicroSD card used by S7-1200 CPUs stores user project files and provides the following critical functions:
  1. Act as the CPU’s load memory: User projects can be stored either on the memory card or in the CPU’s internal storage. If no project is saved inside the CPU, the PLC cannot run without the memory card.
  2. Serve as a medium to transfer project files to multiple S7-1200 PLCs when no programming device is available.
  3. Clear internal CPU projects and protection passwords if the password is forgotten.
  4. Update the firmware version of S7-1200 CPUs (only memory cards with capacity ≥12 MB support this function).

4. SIMATIC Memory Card for S7-1500

S7-1500 CPUs adopt SIMATIC memory cards as program storage media, with core functions listed below:
  1. Work as the CPU’s load memory; the CPU will fail to operate once the memory card is removed.
  2. Support firmware updates for S7-1500 CPUs and central I/O modules.
  3. Read service diagnostic data of the equipment.

5. MicroSD Card for S7-200 SMART

S7-200 SMART CPUs support commercial MicroSD cards with supported capacities of 4 GB, 8 GB and 16 GB. 2 GB and 32 GB cards are not compatible. The supported functions are as follows:
  1. Offline program transmission
  2. CPU firmware upgrade
  3. Restore the CPU to factory default settings
Post time: Jul-31-2026