The redundant system always attempts to restore the previous roles of the R/H CP. The
following applies here: The CPU that last controlled the process becomes the primary CPU.
Requirement: The system time has been set correctly.
After restoring the factory settings, the redundant system assigns the roles according to the
following criteria:
The redundant system compares the following criteria of the two SIMATIC memory cards and
prioritizes the assignment of roles:
•
SIMATIC memory card contains a STEP 7 project
→ High priority
•
SIMATIC memory card is empty and writable
→ Medium priority
•
SIMATIC memory card:
–
missing or
–
inserted, is empty or is not writable
→ Low priority
Result:
If the two R/H CPUs have different priorities, the CPU with the higher priority becomes the
primary CPU.
If the priorities are identical, the R/H CPU with the lower CPU serial number becomes the
primary CPU (see nameplate on the CPU or on the CPU display).
NOTE
If an R/H CPU is in RUN mode, the assigned role does not change when pairing again.
11.3.4 Redundancy IDs
Introduction
For redundant operation, the two CPUs in the redundant system must process identical
project data. In SYNCUP, the operating system copies the content of the SIMATIC memory
card from the primary CPU to the backup CPU.
The load memories contain the project data of both CPUs. This duplication of the project data
is necessary for ensuring redundant operation. By assigning the redundancy IDs, you define
which project data a CPU uses for itself.
Redundancy IDs 1 and 2
Redundant operation is only possible if the two CPUs have different redundancy IDs. The
redundancy IDs can have values of 1 and 2. The CPUs save the redundancy IDs in their
retentive data areas.
Both CPUs have redundancy ID1 in the following cases:
•
Default setting upon initial commissioning
•
After reset to factory settings
252
S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD
Commissioning
11.3 Commissioning procedure
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