About USB memory

Hello everyone,

I am developping software with using Cyclone5 now.

I have one question about USB memory.

With USB controler in HPS and USB3300 PHY chip, I found that there are two type about USB memory.

One is detected and the other is NOT detected.

Linux kernel version is 3.10-ltsi.

Please tell me how to distinguish the USB memory which isn't recognized and a recognized USB memory.