Yes you can change your branch from EC to CS in Second year only if you have completed all the credits prescribed in the first 2 semesters of your studies,in your first attempt, without having had to pass any course requirement in the supplementary examination and/or summer quarter and your CGPA should not be lower than 8.5,at the end of the second semester.Change of branch is made strictly on the basis of inter se merit of the applicants.