Funcationality

The host controller is responsible for USB capabilities on the host side of the bus. It encapsulates a root hub along with a set of ports, onto which devices may be attached externally. Two types of host controllers exist. The first is Intel's Universal Host Controller Interface(UHCI) and the second is the Open Host Controller Interface, backed by Compaq. Each type has its own hardware specification and interface. This project targets the UHCI controller.
The host controller has a set of registers by which it interacts with the outside world.

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COMMAND register: Its role is to act essentially as the control register for USB. It may be used to reset the entire bus, reset the host controller and also to start or stop the execution of the host controller.

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STATUS register: It stores both the status of the host controller and the results of last transfer.

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PORTC & PORTD: The host controller has one register corresponding to each of its ports named PORTC, PORTD etc. These registers store configuration information regarding the respective ports. They may also be used to perform operations on the port. For instance, specified bits on the port store information as to whether a device is attached on the particular port. Other bits may control suspension and activation of the port.

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Apart from this the controller has other registers for configuring the setup and execution of the transfer schedule.