A CDP is a USB port that follows USB BC1.2 and supplies a minimum of 1.5 A per port. A CDP provides power and meets the USB 2.0 requirements for device enumeration. USB-2.0 communication is supported, and the host controller must be active to allow charging. The difference between CDP and SDP is the host-charge handshaking logic that identifies this port as a CDP. A CDP is identifiable by a compliant BC1.2 client device and allows for additional current draw by the client device.

The CDP handshaking process occurs in two steps. During step one, the portable equipment outputs a nominal 0.6-V output on the DP line and reads the voltage input on the DM line. The portable device detects the connection to an SDP if the voltage is less than the nominal data-detect voltage of 0.3 V. The portable device detects the connection to a CDP if the DM voltage is greater than the nominal data detect voltage of 0.3 V and optionally less than 0.8 V.

The second step is necessary for portable equipment to determine whether the equipment is connected to a CDP or a DCP. The portable device outputs a nominal 0.6-V output on the DM line and reads the voltage input on the DP line. The portable device concludes the equipment is connected to a CDP if the data line being read remains less than the nominal data detects voltage of 0.3 V. The portable device concludes it is connected to a DCP if the data line being read is greater than the nominal data detect voltage of 0.3 V.