Usb 2.0 - Intel IXP45X Developer's Manual

USB 2.0 Host Controller—Intel
USB software provides a uniform view of the system for all application software, hiding
implementation details making application software more portable. It manages the
dynamic attach and detach of peripherals.
There is only one host in any USB system. The USB interface to the host computer
system is referred to as the Host Controller. The Host Controller may be implemented in
a combination of hardware, firmware, or software.
There may be multiple USB devices in any system such as hubs, joysticks, speakers,
printers, etc. USB devices present a standard USB interface in terms of comprehension,
response, and standard capability.
The host initiates transactions to specific peripherals, while the device responds to
control transactions. The device sends and receives data to and from the host using a
standard USB data format. The early versions of the USB specification (USB 1.0 and
1.1) operated at 12 Mbps or 1.5 Mbps.
9.3

USB 2.0

The USB 2.0 specification supersedes the earlier versions of the USB specification. USB
2.0 offers a high-speed protocol which offers the user a larger bandwidth and increases
data throughput by a factor of 40. All the peripherals used with the previous versions of
USB work perfectly with USB 2.0 while also offering a larger choice of higher
performance peripherals, such as video-conferencing cameras, next-generation
scanners and printers, a fast storage device, etc.
In addition to the 1.5-Mbps and 12-Mbps data rates of USB 1.1, the evolution from USB
1.1 to USB 2.0 adds an additional data rate of 480 Mbps. Existing USB 1.1 connectors
and full-speed cables support the higher speeds of the USB 2.0 without any changes.
USB 2.0 specifies a microframe, which is 1/8
even at the high data rate.
USB 2.0 system configurations look identical to the end user to configurations based on
earlier revisions of the USB specification. However, the end user will need to distinguish
between USB 2.0 hubs and USB 1.1 hubs to optimize the placement of USB 2.0 high-
speed devices. A USB 2.0 hub accepts high-speed transactions at a faster rate but also
matches the data rate of the peripherals, while the USB 1.1 hub will only support the
lower 12-Mbps and 1.5-Mbps data rates.
August 2006
Order Number: 306262--, Revision: 004US
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IXP45X and Intel IXP46X Product Line of Network Processors
Intel
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of a 1-ms frame allowing small buffers
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IXP45X and Intel IXP46X Product Line of Network Processors
Developer's Manual
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