Onsite we only ever connect to the PLC CPU directly with the MPI cable. 

Maintenance technicians do not have an original copy of the S7 program with comments/symbols etc.

To keep an up to date copy they take an upload from the CPU via MPI connection.

We have remote support from a company in another location, we raised help desk tickets with any issues and they will connect to the CP-343.

My understanding is you cannot take an upload via the CP?

If we made any changes to the program how do the guys doing the remote support ensure they have an up to date copy and how do they get that copy if they can't directly connect. Would any changes made by the maintenance engineers be overwritten if the remote support download their copy.