Hello Aspirant, 

For Architecture application in Tamil Nadu, one must apply for NATA counselling for the colleges. But the thing is that Council of Architecture (COA) does not conduct a centralised counselling instead seat allotment is specifically done by institutes with their own dates of counselling. The architectural intake of Tamil Nadu state is about 3010 seats and increasing. For specific details about college counselling, kindly go through the below mentioned article to help yourself in much better way.

https://www.google.com/amp/s/engineering.careers360.com/articles/nata-counselling/amp

Hope it helped you.!!