What is the difference between cyclic and non cyclic photophosphorylation?

Only photosystem 1 is used in cyclic photophosphorylation where the electrons are passed back to the same photosystem. Non-cyclic phosphorylation uses both photosystems (the electrons are passed via electron carriers to photosystem 1)
Only ATP is produced in cyclic photophosphorylation, whereas both ATP and reduced NAD are produced in non-cyclic.