Functional Sequence Of Link-Up And Update; How To Start Link-Up And Update - Siemens SIMATIC S7-400H Manual

6.2

Functional Sequence of Link-up and Update

There are two types of link-up and update:
• In a "normal" link-up and update the fault-tolerant system should change from
single mode to redundant system mode. The two CPUs then process the
same program in synchronism.
• In the case of a link-up and update with master/standby switch-over, the
second CPU with modified components may take over process control. Either
the hardware configuration or the memory configuration or the operating system
may be modified.
In order to return to redundant system mode a "normal" link-up and update
must be performed subsequently.

How to start link-up and update

Initial situation: Single mode, i.e. only one of the CPUs of a fault-tolerant system
connected via fiber-optic cables is in RUN mode.
Link-up and update to achieve redundant system mode can be initiated as follows:
• change the position of the mode selector on the standby from STOP to RUN or
RUN-P
• POWER ON at the standby (mode selector position RUN or RUN-P), if prior to
POWER DOWN the CPU was not in STOP mode
• operator control at the PG/ES.
You can only start link-up and update with master/standby switch-over
through operator control at the PG/ES.
Notice
If link-up and update on the standby CPU is interrupted (for example, POWER
DOWN, STOP) inconsistent data may result in a Reset request on this CPU.
After the standby is reset link-up and update will be possible again.
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Linking and Synchronizing
6-3