Dear aspirant !  Basically  there is no any base lines to get admission  in engineering  in Tamil  nadu! Its completely  depend upon the examination  level of course! 

The courses like cse and psg ( one of the wanted streams)  to get admission in  these  programs  it is  completely  up to on the cut off level and in which category you are belonging. 

For the courses like cse ,psg , ece in anna university the cut off goes usually  higher  n higher  every year you can compare  with the last year cut off .

Your pcm marks is quite  low to get admission  in anna university  but you are belongs from bcm category   so you calculate  your marks and compare  with cut off  level  .

I hope that this will  help  you !