Festo CPX-FB6 Brief Description page 21

3.5 Start-up behaviour of the CPX terminal
If the M-LED lights up permanently after the system start,
"System start with saved parametrizing and saved CPX
equipment status" is then set.
Caution
In the case of CPX terminals on which the M-LED lights
up permanently, parametrizing will not be carried out
automatically by the higher-order system if the CPX
terminal has been replaced after servicing. In these
cases, check before replacing to see which settings are
required and carry out these settings.
Detailed instructions can be found in the manual for the
field bus node P.BE-CPX-FB6-.. or in the manual for your
handheld.
Festo CPX-FB6 0201NH English 21