23. USB Host Port (UHP)

In the current revision of the AT91SAM9G45 USB High speed is not working. It will work in the processor's next revision, which is expected in august 2011. The Stamp9G45 integrates two USB host ports supporting speeds up to 480 MBit/s. USB Host Port A is connected directly to the transceiver, USB Host Port B is multiplexed with the USB device port. Only one of them can be used at a time.

The controller is fully compliant with the Enhanced HCI(EHCI) specification. It supports both High-speed 480 Mbps and Full-speed 12 Mbps devices.

The USB Host Port (UHP) interfaces the USB with the host application. It handles Open HCI protocol (Open Host Controller Interface) as well as USB v2.0 Full-speed and Low-speed protocols.

The USB Host Port integrates a root hub and transceivers on downstream ports. It provides several high-speed half-duplex serial communication ports. Up to 127 USB devices (printer, camera, mouse, keyboard, disk, etc.) and an USB hub can be connected to the USB host in the USB "tiered star" topology.