This slide highlights how the device contains two interfaces. The second interface is the one most applications will be concerned with, as this controls the four interfaces where data transfer occurs. Note the four endpoint pairs, e.g. 0x02 and 0x82. The direction IN or OUT is defined by the most significant bit of the address. A one is an IN and a zero is an OUT. The first interface is more related to control of data flow setting up session lists for how much data and in which sequence the channels are accessed.