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

System modifications during operation

17.2 Possible hardware modifications

17.2 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 redundant system mode. However, the fault-
tolerant system must be operated temporarily in single mode, because any download of new
hardware configuration data in redundant system mode would inevitably cause it to stop. In
single mode the process is then controlled only by one CPU while you can carry out the
relevant configuration 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 such that you remove 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 both CPUs must be updated several times in the process. It is
therefore advisable to expand the integrated load memory with a RAM card (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 cannot
obtain a RAM card with a capacity to match the FLASH card memory space, split the
relevant 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 reserve 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 continues to be lit even after you have replaced the relevant
synchronization modules, the synchronization cables and even the reserve CPU, there is an
error in the master CPU. In this case, you can, however, switch to the reserve 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, 03/2012, A5E00267695-11
S7-400H