It entirely depends on the vacancy. There is no such cutoff system. If you can secure a good rank, i.e. within the top 300, then you can go for the CSE branch. Otherwise, it entirely depends on the vacancy. If you get a rank of around 1500-3000, and you want  IT or CE, chances of getting admission are low, as most students choose these courses. However, in the counseling, they give a form in which you can fill out your choice of branch and if there are any vacancies later, you can upgrade your branch.