The configuration channel (CC) logic block introduced in the USB-C specification determines cable detection, cable orientation and current-carrying capability. Let’s define these terms:

• Cable detection occurs when one of the two CC lines pulls down (see Figure 3). A DFP will have both of its CC pins pull up with resistor Rp, and a UFP will have both of its CC pins pull down with resistor Rd. Once a DFP processor detects that one of its CC lines is pulled down, the DFP will know that a connection has been made.
• Cable orientation is based on which CC line pulls down (if CC1 pulls down, the cable is not flipped; if CC2 pulls down, the cable is flipped). For nonactive cables, the remaining CC line remains open; for active cables, the remaining CC line will pull down with Ra.
• The values of Rp determine the current-carrying capability. USB-C can natively support either 1.5A or 3A. A DFP can advertise its current-carrying capability with a specific value pullup resistor. A UFP has a fixed-value pulldown resistor (Rd) such that when connected, it forms a voltage divider with Rp. By sensing the voltage at the center tap of the voltage divider, a UFP can detect the DFP’s advertised current.