Link-Up Sequence - Siemens SIMATIC PCS 7 CPU 410-5H System Manual

15.12.1

Link-up sequence

For the link-up sequence, you need to decide whether to carry out a master/standby
changeover, or whether the redundant system state is to be achieved after that.
Link-up with the objective of achieving the redundant system state
To exclude differences in the two subsystems, the master and the standby CPU run the
following comparisons.
The following are compared:
1. Consistency of the memory configuration
2. Consistency of the operating system version
3. Consistency of the contents in load memory
If 1. or 2. are inconsistent, the standby CPU switches to STOP and outputs an error
message.
If 3. is inconsistent, the user program in the load memory in RAM is copied from the master
CPU to the standby CPU.
Link-up with master/standby changeover
In STEP 7 you can select one of the following options:
● "Switch to CPU with modified configuration"
● "Switchover to CPU with modified operating system"
● "Switchover to CPU with modified hardware version"
● "Switchover to CPU via only one intact redundant link"
● "Switching to a CPU with modified PO limit"
Switch to CPU with modified configuration
You may have modified the following elements on the standby CPU:
● The hardware configuration
No blocks are transferred from the master to the standby during the link-up. The exact
circumstances are described in Chapter Switch to CPU with modified configuration
(Page 291).
For information on steps required in the scenarios mentioned above, refer to section Failure
and replacement of components during redundant operation (Page 185).
Note
Even though you have not modified the hardware configuration on the standby CPU, there is
nevertheless a master/standby changeover and the previous master CPU switches to STOP.
CPU 410-5H Process Automation
System Manual, 09/2014, A5E31622160-AB
Supplementary information
15.12 Link-up and update sequence
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