Step 7, Step 8: Changing And Loading User Program - Siemens SIMATIC S7-400H Manual

Modifying the System During Operation
Response if monitoring times are exceeded
If one of the monitored times exceeds the maximum value configured the update is
interrupted. The fault-tolerant system remains in single mode with the previous
master CPU and in certain conditions attempts to perform the link-up and update
later. For more details refer to Section 6.3.
11.4.8

STEP 7, Step 8: Changing and Loading User Program

Initial situation
The fault-tolerant system works with the new hardware configuration in redundant
system mode.
Restrictions
Caution
!
Structural modifications to an FB interface or the instance data of an FB are not
possible in redundant system mode and result in the system mode Stop (both
CPUs in STOP mode).
Procedure
1. Perform all the program modifications relating to the added hardware.
You can add, modify or remove OBs, FBs, FCs and DBs.
2. Load only the program modifications into the PLC.
3. Configure the connections from or to the newly added CPs on both connection
partners and load these into the PLC.
Result
The fault-tolerant system processes the entire system hardware with the new user
program in redundant system mode.
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Automation System S7-400H Fault-tolerant Systems
A5E00068197-07