Difference between APA and ME file?

[Byte-A 0]

Hi all, can anyone explain the difference between the 2 please? I understand that APA is the archived version of the ME file, but what does that mean to the real world user of each file? Can one use one but not the other without the right software or is it another reason?

[Joe E. 259]

The MER file is the runtime file that gets transferred to the PV+. The APA file is an archive of the project. In the "old" days, the MER file could not be restored so you had to use the APA file to transfer the project between computers and needed it in order to make changes. You would then generate and transfer the MER to the PV+. In more recent versions (starting at v5, I think), they added an option to allow/disallow restoring the MER. I remember there being issues early on with the restored MER not including everything (don't remember specifics) but I haven't had any issues with the MER files I've restored lately. If the author of the MER disallowed restoration, you will need the APA file to make changes.

You can replace an HMI (with the same model and at least newer firmware) by just transferring the MER file, which you can do with a flash drive. To make changes, though, you need FactoryTalk View Studio at least as new as the APA/MER file you have.