This temple was built by Rajendra Chola for the royal guru Isanasiva Pandita. Lord referred as Thiru Rameeswaram Udayar. Please refer the above article of Dr R N Sir.
The Jananatha Chathurvedi Managalam referred is the present day Villupuram ( which was Nirupatunga Jayanthangi Chathurvedi Mangalam in Pallava period) and the Rajaraja Chathurvedi Mangalam mentioned is Ennayiram.
This beautiful temple is well maintained by the villagers. It is interesting to note that a new temple was built in the neme of Ramanatha in Rjc period.