Hey there congratulations on scoring 80% in CBSE BOARDS. Yes, with these marks you can get admission in BTech college in Tamil Nadu that provide admission on basis of Boards Marks. You have scored 80 percentile in JEE MAINS and really that will be very helpful to you while getting admission in CSE BTech. You can get admission in Anna University but due to high percentile cutoff, there are very fewer chances of being getting admission in Anna University. but at this rank, you can get admission to very good colleges. If you want any other branches too then even you can get Government Funding Technical Institute (GFTI) like NITs and IIITs and really that will be very helpful to you. You can check your colleges at JEE MAINS College predictor and it will provide you best results along with your home state quota.

https://engineering.careers360.com/jee-main-college-predictor?icn=jee-main-clgpd_landing-page&ici=prediction-section_c360-home