I have notice that PEx (10.4) sometimes updates generated source code files (.h and/or .c) when I "Generate Processor Expert Code" even though the actual content of the file hasn't changed. However, when it does this, it does modify the code generation comment as shown here:
** Date/Time : 2014-07-08, 13:35, # CodeGen: 132
** Date/Time : 2014-07-15, 18:42, # CodeGen: 136
This does not happen all the time nor to all the files. It IS, however, very annoying when you are storing your code in a revision control system. Then, you have to decide between checking in changes that aren't changes (adding noise to RCS metadata/statistics) and spending time and/or effort to "undo" these changes prior to checking in the real changes.
It would be nice if a future version of PEx could fix this problem but in the mean time, if anyone has any ideas about what causes PEx to decide to do this update, I'd appreciate hearing it since this might give a clue about how to prevent this.