Operating Modes Of The Cpus; Operating Modes From Power On To Redundant System Mode; System And Operating Modes Of The Fault-Tolerant System - Siemens SIMATIC S7-400H Manual

5.3

Operating Modes of the CPUs

Operating modes describe the behavior of the CPUs at any given point of time.
Knowledge of the operating modes of the CPUs is useful for programming startup,
the test and the error diagnostics.

Operating modes from POWER ON to redundant system mode

Generally speaking, the two CPUs enjoy equal rights so that either CPU can be the
master or the standby CPU. For reasons of legibility, the illustration presupposes
that the master CPU (CPU 0) is energized prior to the standby CPU (CPU 1) being
energized.
Figure 5-2 deals with the operating modes of the two CPUs from POWER ON up
to redundant system mode. HOLD mode (refer to Section 5.3.5) and
ERROR-SEARCH (refer to Section 5.3.6) are not listed since they are a special
case.
System mode
1.
Stop
Startup
2.
Single Mode
3.
4. Linking
Update
5.
6. Redundant mode
Figure 5-2

System and operating modes of the fault-tolerant system

Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
System and Operating Modes of the S7-400H
POWER ON at CPU 0
Master CPU
STOP
STARTUP
RUN
Updating the user
RUN
program
Updating of dynamic
RUN
data
RUN
POWER ON at CPU 1
Standby CPU
STOP
STOP
STOP
STARTUP/
LINK-UP
UPDATE
RUN
5-5