Link-up and update
12.3 Link-up and update sequence
S7-400H
System Manual, 03/2012, A5E00267695-11
143
12.3
Link-up and update sequence
There are two types of link-up and update operation:
●
Within a "normal" link-up and update operation, the fault-tolerant system should change
over from standalone mode to redundant mode. The two CPUs then process the same
program synchronized with each other.
●
When the CPUs link up and update with master/standby changeover, the second CPU
with modified components can assume control over the process. Either the hardware
configuration, or the memory configuration, or the operating system may have been
modified.
In order to return to redundant system mode, a "normal" link-up and update operation
must be performed subsequently.
How to start the link-up and update operation?
Initial situation: Single mode, i.e. only one of the CPUs of a fault-tolerant system connected
via fiber-optic cables is in RUN.
To establish system redundancy, initiate the link-up and update operation as follows:
●
Toggle the mode selector switch of the standby CPU from STOP to RUN.
●
POWER ON the standby (mode selector in RUN position) if prior to POWER OFF the
CPU was not in STOP mode.
●
Operator input on the PG/ES.
A link-up and update operation with master/standby changeover is always started on the
PG/ES.
NOTICE
If a link-up and update operation is interrupted on the standby CPU (for example due to
POWER OFF, STOP), this may cause data inconsistency and lead to a memory reset
request on this CPU.
The link-up and update functions are possible again after a memory reset on the standby.
