How to Format or Reset an MMC (Micro Memory Card) for SIMATIC S7-300 CPUs?

!! Important Information !!

It is not possible for users to format a SIMATIC Micro Memory Card (MMC).
All you can do is "reset" an MMC, which deletes all user data.

!!! Caution !!!

Do not use the MMC for non-SIMATIC purposes and do not format it with a third-party device ( e.g. using a PC/Laptop MMC Reader. This would possibly overwrite the internal structure of the MMC that cannot be restored. In this case, the MMC is no longer recognized/accepted in a SIMATIC S7-300 CPU and can no longer be used with SIMATIC devices.

1. Resetting a MMC Card using a S7-300:

It is only possible to reset the MMC if it contains data that is invalid for the CPU ( for example, if the data stored is for a different type of CPU).  Otherwise the MMC is only initialized by the procedure described.
 
All the user data is deleted when you reset the SIMATIC Micro Memory Card (MMC). Proceed as follows.

1. Power Off the S7-300 CPU and Insert the MMC into the MMC Slot.
2. Power ON the CPU
3. If the CPU displays slow blinking of the STOP LED then it is not able to read the MMC and is requesting an overall reset.
4. Set the switch to "MRES" and hold it there until the STOP LED lights continuously (approx. 9 seconds).
5. Within the next 3 seconds, you must let the switch go and set it again to "MRES". The STOP LED now blinks during the delete procedure.

If the CPU continues to request an overall reset after the procedure described above, then the MMC is defective.
 
 
2. Resetting a MMC Card using a PG/PC:


The SIMATIC Micro Memory Cards (MMCs) of the S7-300 may be read or written only by the following devices outside the CPU:

• SIMATIC Field PG
• SIMATIC Power PG
• USB prommer (order number 6ES7792-0AA00-0XA0).

Using these devices, you can open an MMC in the SIMATIC



Fig-1 : How to Delete MMC Contents using a SIMATIC PG / USB Prommer