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

9.3.1

Link-up sequence

For the link-up, you need to decide whether to carry out a master/standby changeover, or
whether to conclude the operation by setting the system to redundant state.
Link-up with the objective of setting up system redundancy
To exclude differences in the two subsystems, the master and the standby CPU run
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 standby 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 standby 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/standby changeover
STEP 7 supports the following options:
● "Switch to CPU with modified configuration"
● "Switch to CPU with expanded memory configuration"
● "Switch to CPU with altered operating system"
● "Switch to CPU with modified hardware release"
● "Switch to CPU via only one intact redundant link"
Switch to CPU with altered configuration
You may have modified the following elements on the standby 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 standby during the link-up. For detailed
information, refer to section Switch to CPU with modified configuration or expanded memory
configuration (Page 103).
S7-400H
System Manual, 09/2007, A5E00267695-03
card). The new load memory may be larger or smaller than the old one.
Link-up and update
9.3 Link-up and update
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