Siemens Simatic S7-1500R - Page 265

In general, the two CPUs have equal priority; each CPU can be either primary or backup.
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Figure 11-6System and operating states
The following table provides you with an overview of how the redundant system starts and at
the same time runs through the various operating modes and system states. The following
initial situation and steps are an example.
The operating and system states are described in detail in the following sections.
Table 11-3Redundant system startup
No. in dia
gram
Primary CPU System state Backup CPU
Initial situation: Both CPUs are in STOP operating state. The mode selectors are also in the STOP position.
Step 1: Switch the mode selector of the CPU that is to be primary CPU from STOP to RUN.
①
The CPU switches to STARTUP and
executes startup OB 100 and other
available startup OBs.
STOP → STARTUP The CPU remains in STOP mode.
②
Following successful STARTUP, the
CPU switches to RUN.
The CPU runs like a standard CPU
in RUN and executes the user pro
gram.
STARTUP → RUN-Solo The CPU remains in STOP mode.
Step 2: Switch the mode selector on the backup CPU from STOP to RUN.
265
Commissioning
11.4 Operating and system states
S7-1500R/H redundant system
System Manual, 11/2022, A5E41814787-AD