Hi, can I use to backplanes together using just a Controller cFP-2020 or, if I wish use these two backplanes I'll need to use two Controllers cFP-2020?
cFP can only support 8 cards, so if you have an 8 slot backplane there is no point in getting another. If you have a 4 slot backplane, you can try searching this site to see if NI has some sort of extension cable, but I doubt that. In the future, you should post such questions to the Fieldpoint board, because you will be more likely to get an answer.
The Compact FieldPoint backplanes can not be connected together to allow one controller to control multiple backplanes. You need one controller per backplane.