Dear Koreswar
If you really want to enter into any IITS /nits you need to get at least 240 marks. But if you get more than that you might get enter into the top ones. Please find the below link,  for exact cut off ranks
IIT ECE
All the best.

Please Can you more ellaborate what BC-D is So that we are able to answer your query,

Also let me tell you that to get admission in to IIT and Nit's for the Under graduate programme you need to give the JEE mains and JEE advance exam.