Process Of Link-Up; Link-Up To Achieve Redundant System Mode; Link-Up With Master/Standby Switch-Over - Siemens SIMATIC S7-400H Manual

6.2.1

Process of Link-up

In the link-up process a distinction is made between whether redundant system
mode or a master/standby switch-over is to be achieved.

Link-up to achieve redundant system mode

In order to preclude differences in the two subsystems, the master CPU and the
standby CPU perform the following comparisons.
The following are checked:
1. the identity of the memory configuration
2. the identity of the operating system version
3. the identity of the content of the load memory (FEPROM card)
4. the identity of the content of the load memory (integrated SRAM and RAM card)
If 1., 2. or 3. are not identical, the standby CPU switches to STOP mode with an
error message.
In the case of non-identity of 4. the master CPU copies the user program in the
load memory of its RAM to the standby CPU.
The user program in the load memory of the FEPROM is not copied.
It must be identical before link-up.

Link-up with master/standby switch-over

In STEP 7 you can choose one of the following options and thus release the
following:
• "Switch to CPU with modified configuration"
• "Switch to CPU with expanded memory configuration"
The "Switch to CPU with modified operating system" option cannot be used with
the present operating system versions.
Switch to CPU with modified configuration
You may have made the following memory modifications on the standby CPU:
• the hardware configuration
• the type of load memory (e.g. you have replaced a RAM card with a FLASH
card); the new load memory may be larger or smaller than the old one.
On link-up no blocks are copied from the master to the standby (the exact
circumstances are described in Section 6.2.3.).
The steps to be performed in the above-mentioned scenarios (modification of
hardware configuration, change of type of load memory) are described in
Chapter 11.
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
Linking and Synchronizing
6-7