Hello Heeramani,

CSAB counselling is conducted by NIT Tiruchirappalli and doesn't come under JoSAA. CSAB counselling will start after the end of JoSAA counselling. And yes, you can apply for CSAB Special round counselling but to that you have to first fill up the CSAB registration form in online mode and would have to opt for Special round. Below I have provided the important details regarding CSAB Special Round 2019 - 

CSAB Special Round Eligibility Criteria : 

• The candidates needs to have valid JEE Mains score and should also meet up the JoSAA eligibility criteria 2019.
• The candidates who didn't participated or registered in JoSAA counselling can also apply for special round.
• If the candidates failed to get a seat in JoSAA , they can aslo apply for special round.
• Candidates who got seats in JoSAA but failed to report in the allotted institute or had withdrwan their seats are also eligible to apply for special round.
• The candidates who didn't opted to participate in CSAB counselling after JoSAA are not eligible for special round.

CSAB Special Round Seat Allotment : 

• Registration - Candidates have to register for CSAB Special round 2019 by using their JEE Mains application number and password.
• Fees Payment - After registration is done, the candidates needs to pay the required application fees through SBI MOPS payment gateway.
• Choice filling & Locking - After the payment is done, the candidates needs to fill the name of colleges and branch as per their preference and lock them. 
• Announcement of Seat allotment - The authorities will allot the seats to the candidates on the basis of JEE Main merit,choice filling and seat availability.
• Seat confirmation - The candidates who have been allotted seats needs to confirm by paying the  fees.
• Online reporting to allotted college - Candidates needs to report online to their allotted institute by using their  JEE Main credentials and then uploading the required documents.
• Personal reporting to the allotted institute - Candidates after completing the online reporting, have to physically report to the allotted institute withhin the specified time period.

You can also go through this link and checkout all the details regarding CSAB counselling : https://engineering.careers360.com/articles/csab

Hope I have answered your query. If you still have any doubt then do ask us.

Good Luck !!!