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Overview
Universal Serial Bus (USB) is a bus standard that was originally
specified in 1995. The major goal of USB is to define an expansion
bus that makes it easy to add peripherals to a PC. Today all new
PCs come with one or more USB ports. This has been enabled by the
"Easy
PC Initiative" being led by Microsoft
and Intel,
which is an effort to provide consumers with simpler, easier-to-use
PCs that do not sacrifice connectivity or expandability - and USB
provides exactly this. USB also allows hot swapping of devices on
a home network, without the need of shutting down and restarting
devices.
USB is playing a key role in fast-growing consumer areas: digital
imaging, PC telephony, and multimedia games. The presence of USB
in most new PCs, and its plug-and-play capability, means that PCs
and peripherals (such as CD ROM drives, tape and floppy drives,
scanners, printers, video devices, digital cameras, digital speakers,
telephones, modems, keyboards, mice, digital joysticks and others)
will automatically configure and work together, with a high degree
of reliability, in these exciting new application areas. USB distributes
power to all connected devices and allows bi-directional data transfer,
making it a natural choice for connecting information appliances
across the home. USB opens the door to new levels of innovation
and ease of use for input devices, such as the new generation of
"force-feedback" digital joysticks. There are also brand new opportunities
for all types of peripherals from printers to scanners to high speed
connections such as Ethernet, DSL, cable, and satellite communications.
Introduction to USB 1.1:
USB version 1.1
has gained tremendous success in the marketplace, with most PC and
peripheral vendors worldwide developing products based on this specification.
USB supports two high-speed data transfer protocols: isochronous
and asynchronous. Isochronous connections from the PC USB port to
the peripherals such as scanners, video devices, digital cameras
and printers, supports data transfers at a guaranteed, fixed rate
of delivery of 12 Mbps. The slower asynchronous protocol is used
to communicate with peripherals such as keyboards and mice at 1.5
Mbps.
These data rates of up to 12 Mbps are sufficient for low-speed
to medium-speed peripherals. It replaces many different serial and
parallel connectors at the back of the PC with one standardized
plug-and-play combination, and home networking devices with a USB
port can connect up to 127 different USB peripherals. USB's data
rate also accommodates a whole new generation of peripherals, including
MPEG-2 video-based products, data gloves, and digitizers. Computer-telephony
integration is expected to be a big growth area for PCs, and USB
can provide an interface for ISDN and digital PBXs.
Introduction to USB 2.0:
USB 2.0, is mostly
like USB 1.1, but the next generation specification extends the
bandwidth and hence increases the connection speeds between the
PCs and the peripherals. USB 2.0 has over 40 times the data rate
as USB 1.1 increasing data rates from 12 Mbps to 480 Mbps respectively,
and hence extending its capabilities.
The higher bandwidth will support the most demanding PC applications,
such as digital image creation and Web publishing, where multiple
high-speed peripherals will be running simultaneously. This enables
USB to potentially offer a complete home networking interconnectivity
solution.
Coexistence with IEEE 1394:
USB 2.0 and IEEE 1394, while offer similar data rates primarily
differ in terms of application focus. The USB 2.0 Promoter group
expects USB 2.0 to be the preferred connection for most PC peripherals,
whereas IEEE 1394's primary target is audio/visual consumer electronic
devices such as digital camcorders, digital VCRs, DVDs, and digital
TVs. Both USB 2.0 and IEEE 1394 are expected to coexist on many
consumer systems in the future.
Xilinx Solutions
The Spartan™-II FPGA architecture has enabled a whole new generation
of low-cost high volume solutions. This, combined with a vast portfolio
of soft IP (Intellectual Property) cores allows Spartan-II FPGAs
to provide solutions at a significantly lower cost than ASSPs and
custom ASICs, while offering all of the time-to-market and flexibility
benefits associated with programmable devices. The presentation
provides specific details on how Xilinx solutions enable USB based
home networking.
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