Motorola USB08 - Manual (Page 138)

Designer Reference Manual USB08 Evaluation Board
138 Universal USB Device Driver (USBIO) MOTOROLA
Universal USB Device Driver (USBIO)
E.4 Architecture
Figure E-1 shows the USB driver stack that is part of the Windows 98,
Windows Millennium, and Windows 2000 operating systems. All drivers
are embedded within the WDM layered architecture.
Figure E-1. USB Driver Stack
The following modules are shown in Figure E-1 :
• USB Host Controller is the hardware component that controls the
Universal Serial Bus. It also contains the USB Root Hub.
• OpenHCI.SYS is the host controller driver for controllers that
conform with the Open Host Controller Interface specification.
Optionally, it can be replaced by UHCD.SYS that is the Universal
Host Controller Driver. Which driver is used depends on the
main-board chip set for the PC. For instance, Intel chipsets
contain an Universal Host Controller.
Win32 Application
User Mode
Kernel Mode
USBIO.SYS
Other USB device
drivers
USB Driver Interface (USBDI)
USBD.SYS USBHUB.SYS
OpenHCI.SYS
Hardware
USB Host Controller