Operating Modes Of The Cpus - Siemens SIMATIC S7-400H Manual

System and Operating Modes of the S7-400H
4.3

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 the 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 4-2 analyzes the operating modes of the two CPUs from POWER ON up to
the Redundant system mode. The HOLD mode (refer to Section 4.3.5) and
ERROR-SEARCH (refer to Section 4.3.6) are not listed since they are a special
case.
System mode
1.
Stop
Startup
2.
3. Solo mode
4. Link-up
Update
5.
6. Redundant mode
Figure 4-2 System and Operating Modes of the Fault-tolerant System
4-6
POWER ON at CPU 0
Master CPU
STOP
STARTUP
RUN
Updating the user
RUN
program
Updating of dynamic
RUN
data
RUN
S7-400H Programmable Controller Fault-Tolerant Systems
POWER ON at CPU 1
Standby CPU
STOP
STOP
STOP
LINK-UP/
STARTUP
UPDATE
RUN
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