Link-Up Sequence - Siemens SIMATIC S7-400H System Manual

12.3.1

Link-up sequence

For the link-up sequence, you need to decide whether to carry out a master/reserve
changeover, or whether redundant system mode is to be achieved after that.
Link-up with the objective of setting up system redundancy
To exclude differences in the two subsystems, the master and the reserve 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 load memory (FLASH card) content
4. Consistency of load memory (integrated RAM and RAM card) content
If 1., 2., or 3. are inconsistent, the reserve CPU changes to STOP mode and outputs an error
message.
If 4. is inconsistent, the master CPU copies the user program from its load memory in RAM
to the reserve CPU.
The user program stored in load memory on the FLASH card is not transferred.
It must be identical before initiating link-up.
Link-up with master/reserve changeover
In STEP 7 you can select one of the following options:
● "Switch to CPU with modified configuration"
● "Switchover to CPU with expanded memory configuration"
● "Switchover to CPU with modified operating system"
● "Switchover to CPU with modified hardware version"
● "Switchover to CPU via only one intact redundant link"
Switch to CPU with modified configuration
You may have modified the following elements on the reserve CPU:
● The hardware configuration
● The type of load memory (for example, you have replaced a RAM card with a FLASH
The master does not transfer any blocks to the reserve during the link-up. For detailed
information, refer to section Switch to CPU with modified configuration or expanded memory
configuration (Page 152).
S7-400H
System Manual, 03/2012, A5E00267695-11
card). The new load memory may be larger or smaller than the old one.
Link-up and update
12.3 Link-up and update sequence
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