RFID reader with TRF7960 and PIC24FJ128GA010

Hi, I'm new with RFID technology. I'm trying to make a RFID reader with TRF7960 + PIC24FJ128GA010. I made the circuit in the datasheet page 10 (spi mode with slave select).

What are steps that I must follow to read a RI-TH1-CB1A-00 transponder?. What do I do first?. I readed that I need to configurate the reader with the appropiate ISO protocol, what's the correct configuration for this transponder?.

For example, when I want configurate the reader I send:

ss=0;

write_spi(0x00);

write_spi(0x20);

write_spi(0x01);

write_spi(0x85);

ss=1;

But, when I try to read the ISO register I get 0x00.

ss=0;

write_spi(0x61);

iso_data = read_spi();

ss=1;

In all cases the MSB is first, please give me instructions  to write and read registers of the reader.