USB Host Controller Interfaces
The intent of USB was to provide a standardized Plug-N-Play interface
that would permit USB-compliant devices from any manufacturer to
coexist peacefully with those from any other maker. The ball got
rolling in September 1995, when 25 major PC companies announced the
formation of a consortium to develop a non-proprietary, open
Host Controller Interface (HCI) standard. This
was necessary because the HCI was not defined in the USB
specification itself. Although it would have been possible for each
motherboard or chipset manufacturer to develop a proprietary USB HCI,
that would have introduced serious compatibility issues between the
multiple HCIs and USB peripherals. So, for the good of the industry
and in the interests of interoperability, nearly all of the major
players in the PC industry signed on to this initiative.
The HCI is the heart of USB, just as the chipset is the heart of a motherboard. In fact, the USB HCI is often referred to as the USB chipset. Just as the system chipset defines the functionality and capabilities of the motherboard, coordinates the working of other motherboard components, and arbitrates conflicting demands, a USB HCI chipset defines the USB and performs analogous services for connected USB peripherals.
The HCI may reside in any or all of three places:
- Embedded in the motherboard chipset
All modern chipsets contain a USB 1.1 HCI embedded in the Southbridge. The quality and compatibility of the embedded HCI depends on the ...