USB 3.0

USB 3.0 is physical SuperSpeed bus combination in parallel with a physical USB 2.0 bus(see in figure).It has similar architecture components as USB 2.0.

The USB 3.0 interconnect is the manner in which USB 3.0 and USB 2.0 devices connect to and communicate with the USB 3.0 host. The USB 3.0 interconnect inherits core architecture elements from USB 2.0,although several are augmented to accommodate the dual bus architecture.

The baseline strucutral topology is same as USB 2.0. It consists of a tiered star topology with a single host at tier 1 and hubs at lower tires to provide bus connectivity to devices.

The USB 3.0 connection model accommodates backwards and forward compatibility for connecting USB 3.0 or USB 2.0 devices into a USB 3.0 bus. similarly, USB 3.0 devices can be attached to a USB 2.0 bus. The mechanical and electrical backward/forwards compatibility for USB 3.0is accomplished via a composite cable and associated connector assembles that from the dual-bus architecture.USB 3.0 devices accomplish backward compatibility by including both SuperSpeed and non-SuperSpeed bus interface which are essentially parallel buses that may be active simultaneously.

The USB 3.0 connection model allows for the discovery and configuration of USB devices at the highest signaling speed supported by the device, the highest signaling speed supported by all hubs between the host and device,and the current host capability and configuration.

USB 3.0 hubs are a specific class of USB device whose purpose is to provide additional connection points to the bus beyond those provided by the host. In this specification, non-hub devices are referred to as peripheral devices in order to differentiate them from hub devices. In addition , in USB 2.0 the term “function ” was sometimes used interchangeably with device. In this specificaton a function is a logical entity within a device.