Thanks for your reply.
The reason that I want to replace NCU from 572.3 to 572.5 is that NCU572.3 has cancelled since 2006 and I can't be supplied with it any more from SIEMENS.
My customer doesn't have enough NCU572.3s which can be replaced in emergency. (We are only supplied with NCUx.5 from SIEMENS)
So, I have to upgrade NCU as soon as possible before something is happened(for emergency)
And I performed Upgrading NCU under the Upgrading manual - I attach this manual as attachment.
I already performed upgrading NCU to x.5 several times and it worked out well.
I know what kind of PLC is in each NCU type.
If Upgrading NCU which is programmed 'SI' is not normal and easy thing and needs recommissioning, SIEMENS has to provide all version of NCUs. If not, Siemens has to give us correct manual to be able to succeed this work without problem like thing that I mentioned in this forum.