Siemens SIMATIC ET 200SP System Manual page 216

To reset the CPU memory using the mode selector, proceed as follows:
1. Set the mode selector to the STOP position.
Result: The RUN/STOP LED lights up yellow.
2. Set the mode selector to the MRES position. Hold the selector in this position until the
RUN/STOP LED lights up for the 2nd time and remains continuously lit (this takes three
seconds). After this, release the switch.
3. Within the next three seconds, switch the mode selector back to the MRES position, and
then back to STOP again.
Result: The CPU executes memory reset.
For information on resetting the CPU to factory settings, refer to the section Resetting the
CPU to factory settings (Page 249).
Procedure using STEP 7
For a memory reset of the CPU using STEP 7 proceed as follows:
1. Open the "Online Tools" task card of the CPU.
2. Click the "MRES" button in the "CPU control panel" pane.
3. Click "OK" in response to the confirmation prompt.
Result: The CPU switches to STOP mode and performs a memory reset.
Distributed I/O system
System Manual, 09/2019, A5E03576849-AJ
Commissioning
11.7 CPU memory reset
215