NCAA ruling?

I was watching tape on the GT vs MIA. During the game Mia intercepted the ball in the end zone. A flag was thrown for DPI (in the end zone). The DB that intercepted the pass ran all over the end zone and at one point step one foot onto the field. Then back into the end zone where he was tackled on the end line. I don't know NCAA rules but does that one foot count as being out of the end zone?