s7-1214c; 1212 does not let to modify a program/download new program

Are all 7 PLC programs exactly the same except for very minor differences, or are they 7 completely unique programs, or are some of them very similar and some very different?

Do they all have identical hardware modules and profinet devices connected?  Were they all commissioned at the same time?

There are many bugs in the earlier versions of TIA Portal (V10.5..V11..V11SP1...V11SP2...V12...V12 SP1 and all the hotfixes and updates).  There are often bugs introduced and carried over during upgrades from older to newer versions.  I have seen bugs carried over from V10.5 SP2 all the way to V14 SP1 where I essentially had to recreate the hardware configuration manually in a new V14 SP1 project, then drag in the software / tags and everything else from the project tree before I could upgrade to V15.

Are all 7 PLCs running the exact same firmware?  Are all 7 PLCs the exact same part #?  DC/DC/DC or AC/DC/DC or DC/DC/RLY and so on?

There quite a few reasons the problems could be isolated to a subset of the entire set of PLCs.

For example, if someone using V11 created PLC_1 and everything works great.  They open PLC_2 and suddenly V11 starts leaking memory and eventually crashes.  Then they restart V11 instead of restarting Portal (this is V11 after all).  Now they edit PLC_2 and save the project.  Somehow the crash messed up something inside portal and that causes PLC_2 project to have something messed up in it that does not affect its operation, but does affect the upload/download comparison.  Now when PLC_2 is downloaded, it is only functional when used on the original PC. I am not saying this is fact, but experience tells me it is not fiction.

The fix is to upload the software, tags and anything else you can to a brand new V12 project where the hardware configuration has been created manually and configured exactly as the original V11 project.  Now compile / rebuild all for hardware and software.  Then DOWNLOAD to the PLC the new V12 project over top of the original being sure to save the current DB and tag values that matter for the system to start back up right where it left off.

Do that for all 5 of the unhappy PLC projects and you can support them.

Then backup/archive the projects so they can be used by anyone using V12.

It is very difficult to find 7 PLCs with the exact same hardware / firmware revisions, especially that old.  Siemens made changes early on because there were bugs that needed fixed.

chm0

sir, it's all very good, but does not explains why problems occurred only on 2 PLCs of 7...

The "someone" knows answer is found only by contacting Siemens Support directly using Support Request -> create new request.

Since the software is so old (V12), they may say it is no longer supported and not tell you the answer to your question about what those hex error codes mean.

If the PLC is running correctly, there is nothing wrong with the currently in-use flash memory or it would not be running.

If you have tried my suggestions about building a new project using all the existing blocks, compile / rebuild all and it still refuses to download, then you can go online and reset the plc to factory defaults, then you can install the newly created project.

I personally would not do that without a spare PLC of the exact same part # available in case the plc refuses to accept new programming after a factory reset.  Odds are low, but I would not want to leave with a machine not running because of advice from an online forum posted by another Siemens user just like me.