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The RUN/STOP LED is on (constant yellow light)The following table provides an overview of the contents of the memory objects after
memory reset.
Table 9- 15 Memory objects after memory resetThe CPU executes an automatic memory reset if an error occurs that prevents normal
further processing.
Examples of such errors:
● User program is too large and cannot be loaded to the work memory in full.
● The project data on the SIMATIC memory card are damaged, for example because a file
was deleted.
● You remove or insert the SIMATIC memory card. The backed-up retentive data differs in
structure from the data in the configuration on the SIMATIC memory card.
● SYNCUP aborts in the backup CPU. You can find more information in the section
SYNCUP system state (Page 205).Memory reset is required to reset the primary or backup CPU to its "initial state". Memory
resets can only be run in the STOP operating state of a CPU.
CPU memory reset
There are three options for performing a CPU memory reset:
● Using the mode selector
● Using the display
● Using STEP 7The procedure described below also corresponds to the procedure for resetting to factory
settings:
• Selector operation with inserted SIMATIC memory card: CPU executes a memory reset
• Selector operation without inserted SIMATIC memory card: CPU executes reset to factory
settingProceed as follows for a CPU memory reset using the mode selector:
1. Set the mode selector master interface module to STOP.
Result: The RUN/STOP LED lights up yellow.
2. Set the mode selector master interface module to MRES. 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). Then release the switch.
3. Within the next three seconds, switch the mode selector back to the MRES position and
then back to STOP.
Result: The CPU executes a memory reset.
For information on resetting the CPU to factory settings, please refer to the section Resetting
CPUs to factory settings (Page 277).
Procedure using the display
To navigate to the required "Memory reset" menu item, select the following sequence of
menu commands and confirm each selection with "OK".
● Settings → Reset → Memory reset

Result: The CPU executes a memory resetRequirement: There is an online connection between the CPU ad PG/PC.
Proceed as follows for a CPU memory reset with STEP 7:
1. Open the "Online Tools" task card of the CPU.
2. Click "MRES" in the "CPU operator panel" pane.
3. Click "OK" in response to the confirmation prompt.
Result: The CPU executes a memory reset.
9.6 Backing up and restoring the CPU configuration
Backup from online device
You may make changes in the operation of your plant. For example, you may add new
devices, replace existing ones or adapt the user program. If these changes result in
undesirable behavior, you can restore the plant to an earlier state. Before you download a
changed configuration to the CPU, first use the option "Backup from online device" to create
a complete backup of the current device state.You may make changes in the operation of your plant. For example, you may add new
devices, replace existing ones or adapt the user program. If these changes result in
undesirable behavior, you can restore the plant to an earlier state. Before you download a
changed configuration to the CPU, first use the option "Backup from online device" to create
a complete backup of the current device state.
With the option "Upload from device (software)", you load the software project data from the
CPU to an existing CPU in the project.
Upload device as new station
If you are operating a new PG/PC in the plant, the STEP 7 project that was used to create
the plant configuration might not be available. In this case, you can use the option "Upload
device as new station" to load the device data to a project in your PG/PC.
Snapshot of the actual values
To allow you to restore the actual values at a later date, back up the actual values of the
data blocks using the option "Snapshot of the actual values".The table below shows the backup of CPU data depending on the selected type of backup
and its specific characteristics:The following example shows how to carry out a complete backup of the current device state
of the CPUs in STEP 7. The R/H redundant system is in the RUN-Solo system
state.
1. Right-click to select the R/H system in the project tree.
2. Select the "Backup from online device" command from the shortcut menu.
The "Upload preview" dialog window sets out the key information on the backup process to
be run:The preview shows that the backup target is H-System_1.
For a backup, the redundant system R/H must be in the STOP system state.
In the "Action" column, select the "Stop module" command from the drop-down menu.Click "Upload from device" to start the backup.
Reference
You can find more information on the various types of backup in the STEP 7 online help.
Emergency address (emergency IP)
If you cannot access the CPU via the IP address, you can set a temporary emergency IP
address for the CPU. To the more information on emergency address options, please refer
to the CommunicationDifferent categories of texts are created when you configure a CPU,