Thank you for the info. Yes I have access to the secure files.
The most confusing is that FCCU monitoring is OPTIONAL for FS26xyB (table 5 of this safety manual "SM616130-FS26 Safety Manual 3.0(3.0).pdf" )
Same as in Table 1 of "DS616030-FS26 Product Datasheet 3.0(3.0).pdf"
It suggests that the FCCU function can be enabled somehow, but it is not in the OTP configuration.
From your answer I conclude that there isn't any reaction on the state of the FCCU pins in the FS2603B device.
