usb software architecture

Each has only one USB host, which comprises the following layers:
Bus Interface
USB bus interface processing electrical interconnect layer and protocol layer. From the perspective of the interconnect, similar to the bus interface and the host computer at the same time is given by the device, e.g., a serial interface engine (SIE). USB bus interface is implemented by the host controller.
USB data transfer between the main controller system management host and USB devices. It is dependent on the interface between the host controller hardware to define the primary controller. At the same time, the system also manages USB USB resources, such as bandwidth and bus energy, which allows customers to access the USB possible. There are three basic components USB System:
Host controller driver (HCD) which can be mapped to different devices to the USB host controller system. And USB interfaces called HCD between HCDI, specific HCDI defined by the host controller supports different operating systems, Universal Host Controller driver (UHCD) at the bottom of a soft structure, it is managed and controlled by the main controller. UHCD achieved with the USB host controller USB host controller to communicate and control, and other parts of its system software is hidden. System software in the highest level software interface controller to communicate with the main UHCD through.
USB driver (USBD) UHCD it on the drive, which provides drive-level interface to meet the existing device driver design. USBD to the I / O request packets (IRPs) provided in the form of data transmission infrastructure, which consists of a specific demand by the pipe (Pipe) data transmission components. In addition, USBD enable a client device appears abstract to abstract and management. As part of the abstract, USBD have the default pipeline. It gives you access to all of the USB devices for standard USB control. The default pipe describes a USBD between USB devices and logical channel communications.
Host Software
In some operating systems do not provide USB system software. The software was originally used to provide configuration information and load the configuration to the device driver. In these operating systems, device drivers, applications will interface instead of directly accessing USBDI (USB driver interface) structure.
USB Client Software
It is located on the software architecture of the highest level, is responsible for handling specific USB device driver. Client layer describes all direct role in the device's software entrance. When the device is detected the system, these clients will have a direct effect on the peripheral hardware. This shared feature of the USB system software is placed between the customer and its equipment, which would be based on the client device image USBD formed it by the client for processing.
Host layers have the following functions:
To detect the connection and remove the USB device.
Data flow management host and USB devices.
USB connection status and activity statistics.
Control electrical interface between the host controller and USB devices, including a limited supply of energy.
HCD provides an abstract perspective abstract master controller and USB host controller transmitted through the data. USBD provides an abstraction between abstraction and USBD client and USB function USB devices for data transmission. USB system facilitates data transfer between client and function, and as a control point specification interface USB devices. USB buffer management system provides the ability to synchronize data transmission and allows the customer and functional requirements.
Hardware Structure Editor
USB four-wire cable, two of which are used to transmit serial data channel downstream (Downstream) equipment to provide power for the other two, has been successfully connected to any peripherals and mutual recognition, both devices will be able to support both the maximum data transfer rate. USB bus automatically switched according to the situation in the peripheral compatible transmission mode from a high to low dynamic and match locked at an appropriate rate. USB is based on the token bus. Similar to Token Ring or FDDI network based on token bus. USB host controller broadcast token, token devices on the bus to detect whether an address is consistent with itself, by receiving or sending data to the host response. By supporting USB suspend / resume operations to manage USB bus power. USB system using cascaded star topology, the topology consists of three basic components: the host (Host), Hub (Hub) and functional equipment.
Host, also known as the root, root or root knot Hub, do it on the motherboard or as data on the USB bus adapter cards installed on a computer, the host contains a host controller and root hub (Root Hub), and controls control the flow of information, the system can only have one of each USB root hub, which is connected to the main controller, a computer may have more than one root hub.
USB hub is the structure of a specific component, which provides named port (Port) of points device is connected to the USB bus, the simultaneous detection of connected devices on the bus, and these devices provide power management, fault detection and recovery responsible for bus . Hub can provide energy for the bus, can provide energy for themselves (obtained from an external power supply).
Function device is connected via the bus port. USB Hub at the same time do use.