Possible Hardware Modifications - Siemens SIMATIC S7-400H System Manual

System modifications in operation

14.2 Possible hardware modifications

14.2 Possible hardware modifications
How is a hardware modification made?
If the hardware components concerned are suitable for unplugging or plugging in live, the
hardware modification can be carried out in the redundant state. However, the fault-tolerant
system must be operated temporarily in single mode, because any download of new hardware
configuration data in redundant mode would inevitably cause it to STOP. The process is then
controlled only by one CPU, while you can carry out the relevant changes at the partner CPU.
During a hardware modification, you can either remove or add modules. If you want to alter
your fault-tolerant system in such a that you remove some modules and add others, you
have to make two hardware changes.
NOTICE
Always download configuration changes to the CPU using the "Configure hardware" function.
Load memory data of the redundant CPUs must be updated several times in the process. It
is therefore advisable to expand the integrated load memory with a RAM module, at least
temporarily.
You may only change the FLASH card to a RAM card as required for this if the FLASH card
has as much maximum storage space as the largest RAM card available. If you can not
obtain a RAM module with a capacity to match the FLASH memory space, split the relevant
actions in your configuration and program modifications into several smaller steps, in order
to provide sufficient space in the integrated load memory.
Synchronization link
Whenever you make hardware modifications, make sure that the synchronization link
between the two CPUs is established before you start or turn on the standby CPU. If the
power supply to the CPUs is on, the LEDs IFM1F and IFM2F that indicate errors on the
module interfaces on the two CPUs should go off.
If one of the IFM LEDs lights up again, even after you have replaced the relevant
synchronization modules, the synchronization cables and even the standby CPU, there is a
problem on the master CPU. In this case, you can, however, switch to the standby CPU by
selecting the "via only one intact redundancy link" option in the "Switch" STEP 7 dialog box.
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WARNING
System Manual, 09/2007, A5E00267695-03
S7-400H