RFID FX7500 Antennas Issue

Hi, I am using FX7500 RFID readers with 4 antenna's and I have compiled RFIDSample4App.c and common.c in our controller and connected with the reader and getting the tag data from 1 antenna using SimpleInventory(...) function. I am not able to get the data from all the antennas. Please help me how can we tag data from all the four antennas simultaneously?