Specifics Of The Cpus Of The Redundant System S7-1500R/H - Siemens S7-1500 Function Manual

Memory areas and retentive memory
2.1 Memory areas
Additional memory areas
Besides the memory areas that have been described for the user program and data, the
CPU has additional memory areas available.
The additional memory areas include the following:
● Process images
● Temporary local data
The CPU-specific sizes can be found in the technical specifications for the respective CPU.
2.1.1

Specifics of the CPUs of the redundant system S7-1500R/H

The redundant system S7-1500R/H consists of two CPUs. A SIMATIC memory card must be
inserted in each of the CPUs. During redundant operation, both CPUs execute the user
program in parallel. In so doing, one CPU takes the role of the leading CPU (Primary CPU)
and one CPU takes the role of the following CPU (Backup CPU). If one CPU fails, the
second CPU maintains control over the process.
Memory areas
The two CPUs of the redundant system S7-1500R/H have the same memory areas as the
CPUs of non-redundant systems.
You create the hardware configuration of the offline project data only once in STEP 7
STEP 7 loads the offline project data into the current primary CPU. The system synchronizes
all data required for redundant operation from the primary CPU to the backup CPU.
Both CPUs receive identical online project data. The online project data contains the
hardware configuration of the H-system.
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Structure and Use of the CPU Memory
Function Manual, 10/2018, A5E03461664-AC