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How do you format or reset an MMC (Micro Memory Card) for SIMATIC S7-300 CPUs? Keywords: Reset MMC, Format MMC April 2008

Instructions:
It is not possible for users to format an MMC. All you can do is "reset" an MMC, which deletes all user data. Proceed as follows.

  1. The MMC is slotted in the bay of the CPU. Your CPU requests an overall reset (slow blinking of the STOP LED).
  2. Set the switch to MRES and hold it there (approx. 9 seconds) until the STOP LED lights continuously.
  3. 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 MMC continues to request an overall reset after the procedure described above, then it is defective.

Note:
It is only possible to reset the MMC if it contains data that is invalid for the CPU. Otherwise the MMC is only initialized by the procedure described.

Warning:Do not use the MMC for non-SIMATIC purposes and do not format it with a third-party device. 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 CPU and can no longer be used with SIMATIC devices.


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