Since Unity Pro V4.0 when used in a DFB section the RETURN instruction has the following behavior:

• Using simulation mode whatever the language , or using standard mode when the DFB section is ST, IL or LD (with the project setting : « Generate with LD link animation » unselected) :
  • RETURN instruction forces the return to the program which called the DFB. The rest of the DFB section containing the RETURN instruction is not executed. The next sections of the DFB are not executed. The program which called the DFB will be executed after return from the DFB. (as mentioned in Unity Pro Help
    
• Using standard mode when the DFB section is FBD or LD (with the project setting : « Generate with LD link animation » selected )
  
  • RETURN instruction forces the return to the next sections of the DFB. The rest of the DFB section containing the RETURN instruction is not executed but the next sections of the DFB are executed.

Before  Unity Pro V4.0

• Using simulation mode whatever the language :
  • RETURN instruction forces the return to the program which called the DFB. The rest of the DFB section containing the RETURN instruction is not executed. The next sections of the DFB are not executed. The program which called the DFB will be executed after return from the DFB.
    
• Using standard mode whatever the language :
  • RETURN instruction forces the return to the next sections of the DFB. The rest of the DFB section containing the RETURN instruction is not executed but the next sections of the DFB are executed.

Released for: Schneider Electric Malaysia