Some issues: RSSI and loss packet rate

I wanted to make two different questions:
First, how to measure the RSSI of my Xbee S2. Have I got to connect pin 6 to an analog input? I really want to view the RSSI on Processing or some program. I understand that I set the pin 6 as: RSSI PWM OUTPUT, and from there connect it to an analog input pin of the same Xbee, correct?
Another point: I want to know is if I can calculate the packet loss rate with Xbee?