Siemens SIMATIC S7-1500 System Manual page 275

The communication connections in the primary CPU are temporarily ended. You can no
longer delete, load, generate or compress blocks in the user program. You can no longer run
any test or commissioning functions.
Table 11-8 Preparing the copying of the work memory
④
Copying the work memory
The primary CPU stores a consistent snapshot of its memory contents and some system
memory contents (backup CPU dump) at the next cycle control point: Process image, bit
memory, SIMATIC time/count functions, temporary local data, data block contents.
After the snapshot, the primary CPU immediately resumes user program execution.
Communication connections are reestablished and asynchronous instructions are started.
The primary CPU copies the consistent snapshot to the backup CPU and continues operating
in parallel. Data blocks, the process image, etc. are immediately overwritten with current data
from the primary CPU.
S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD
Primary CPU
RUN-Syncup
Syncup...
Preparing for transfer
of work memory.
Step 3 of 5
Commissioning
11.4 Operating and system states
Backup CPU
CONNECTING...
Overview
CPU 1517H-3 PN
6ES7 517-3HP00-0AB0
?
?
OK
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