will use HNP to switch to the slave role, with the camera becoming the host so pictures stored on the camera can be printed out without reconnecting the cables. The new OTG protocols cannot pass through a standard USB hub since they are based on electrical signaling via a dedicated wire. The USB OTG and Embedded Host Supplement to the USB 3.0 specification introduces an additional communication protocol: Role Swap Protocol (RSP): RSP achieves the same purpose as HNP (i.e., role swapping) by extending standard mechanisms provided by the USB 3.0 specification. Products following the USB OTG and Embedded Host Supplement to the USB 3.0 specification are also required to follow the USB 2.0 supplement in order to maintain backwards compatibility. SuperSpeed OTG devices (SS-OTG) are required to support RSP. SuperSpeed Peripheral Capable OTG devices (SSPC-OTG) are not required to support RSP since they can only operate at SuperSpeed as a peripheral; they have no SuperSpeed host and so can only role swap using HNP at USB 2.0 data rates. Device roles USB OTG defines two roles for devices: OTG A-device and OTG B-device, specifying which side supplies power to the link, and which initially is the host. The OTG A-device is a power supplier, and an OTG B-device is a power consumer. In the default link configuration, the A-device acts as a USB host with the B-device acting as a USB peripheral. The host and peripheral modes may be exchanged later by using HNP or RSP. Because every OTG controller supports both roles, they are often called "Dual-Role" controllers rather than "OTG controllers". For integrated circuit (IC) designers, an attractive feature of USB OTG is the ability to achieve more USB capabilities with fewer gates. A "traditional" approach includes four controllers, resulting in more gates to test and debug: USB high speed host controller based on EHCI (a register interface) Full/low speed host controller based on OHCI (another register interface) USB device controller, supporting both high and full speeds Fourth controller to switch the OTG root port between host and device controllers Also, most gadgets must be either a host or a device. OTG hardware design merges all of the controllers into one dual-role controller that is somewhat more complex than an individual device controller. Targeted peripheral list (TPL) A manufacturer's targeted peripheral list (TPL) serves the aim of focusing a host device towards particular products or applications, rather