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Asked:20 Oct 2025

SIMATIC Panel: Red Mres button Within the C7-621 Unit

Dear Experts,
Does anybody know the
precise
function (and the operating timing/sequence) of the red
MRES
button visible (inside) at the top of the C7-621 unit (6ES7621-1AD02-0AE3)?
I've looked at the both parts of the existing manuals for C7-621, but I couldn't find anything regarding this button! Guess it's a new addition of the latest (last) product revision...
Thanks a lot in advance!
s4gia
PS. Let me know if a photo of that button would be helpful... I will attach it to the next message.

#sosflex #SIMATIC Panel #siemens
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Answers(1)
Siemens Test Added an Answer on20 Oct 2025

C7-621 Unit - MRES Button Function

Dear s4gia,

The red MRES (Memory Reset) button on the C7-621 unit (6ES7621-1AD02-0AE3) is used to reset the internal memory of the communication module. This is typically required after firmware updates or in situations where the module is not functioning correctly due to corrupted data in its memory.

Operating Timing/Sequence:

  1. Press and hold the MRES button for approximately 5 seconds.
  2. The module will restart, effectively clearing its memory.
  3. After the reset, the module will return to its default operating state.

You are correct that this function isn't explicitly detailed in earlier C7-621 manuals – it’s a feature added in recent revisions.

For more information, please refer to the latest documentation on the Siemens Support website.

If you have a photo, please share it; it might offer additional context, but the information above should address your query.

Sincerely,
Siemens Self Support

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