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Digital
Communication
Tutorials
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&
Introduction
of USB |
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Since
original
IBM made
computers,
many new
devices
have come
up which
were not
thought of
at that
time.
Scanners,
portable
hard
drives,
Zip
drives,
and
force-feedback
joysticks
are just a
few
examples
of devices
appearing
on the
desktop.
Attempts
have been
made to
provide
four to
eight
serial
ports on a
single PC,
there was
no real
standard
that
gained
widespread
acceptance.
SCSI
seemed to
be the
solution
of choice
for many
vendors of
scanners
and
external
drives,
however,
interface
cards and
devices
were
expensive
and the
standard
lacked
complete
unity.
Therefore,
many began
work on
specifications
for new
interconnecting
solutions,
such as
IEEE 1394
and USB.
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The
Solution:
USB
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Though
slower
than IEEE
1394, USB
still
boasts a
data rate
of 12 Mbps
(mega-bits
per
second)
and allows
you to
connect up
to 127
devices to
your PC!
It is
designed
to support
modems,
keyboards,
mice, 4x
– 6x CD
ROM
drives,
joysticks,
tape/floppy/hard
drives,
scanners
and
printers.
In
addition,
a new wave
of
peripherals
such as
telephones,
digital
speakers,
digital
snapshot
and motion
cameras,
data
gloves and
digitizers
are to
take
advantage
of this
exciting
and
versatile
new
interface
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How USB
Port looks
on my
Computer?
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Look for
something
like this
on your
Computer.
These are
2 USB
ports. And
below is
the Plug
you will
find on
one of the
USB device
you may
have:
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Symbol of
USB
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While
discussion
on USB
ports or
devices,
above
symbol is
used.
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Advantages
of USB
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"Hot
Plugging"
which is
the
ability
for
plugging
and
unplugging
a device
without
powering
down,
comes with
USB.
USB
devices
are
self-identifying,
and USB is
Plug-and-Play
compliant,
which
means that
installation
and
configuration
of USB
peripherals
will be
relatively
easy. USB
cables
also carry
power, so
you don't
need extra
cables or
transformers.
USB ports
on your
computer
will work
with any
USB
peripheral
that you
want to
plug into
it. USB is
also "Hot-Wwappable",
means you
can plug
devices in
or out
without
turning
off the
computer
A
standardized
plug
interface
means
convenient
and
headache-free
addition
of new
peripherals.
The same
plug is
used for
different
types of
devices so
you
don’t
have to
worry
about an
adapter
for the
mouse or
video
camera.
Since USB
is an
industry-wide
and Royalty-Free
open
standard,
everyone
can
develop
USB
devices.
This ends
the need
for
proprietary
interfaces
and
guarantees
cross-vendor
compatibility.
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Disadvantages?
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One
known
disadvantage
is that,
it has to
use a
Windows98
or higher
operative
system and
Windows NT
doesn't
support
USB
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Accessibility
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You can
simultaneously
connect up
to 127
devices to
your PC,
with cable
connections
reaching
five
meters in
length.
This means
that the
number of
devices
you can
have is
not
limited to
the number
of ports
at the
back of
your PC,
nor is it
limited to
the space
of your
desktop
since you
can place
devices
quite far
from the
host.
Its
Plug and
Play
features
and
Iinclusion
of
software
and driver
requirements
as part of
the USB
specification
ensures
Plug and
Play
functionality.
Since most
of the
intelligence
needed to
manage the
USB
devices is
software
based,
peripherals
are
simpler to
design and
produce,
and this
efficiency
translates
into lower
costs for
the
consumer.
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More on
USB:
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The
USB2
Enhanced
Host
Controller
Interface
(EHCI)
defines a
Debug Port
interface
that
provides a
viable
alternative
for kernel
debugging
on
legacy-free
platforms.
The USB2
Debug
Device
Functional
Specification
(PDF, 305
Kb)
provides a
detailed
description
of the
device
framework,
commands,
and other
operational
requirements
of a USB2
Debug
Device
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The
USB 2.0
spec and
additional
information
concerning
the spec
can be
downloaded
for free
from
within the
official
USB-IF web
site at www.usb.org/developers/docs/.
The USB
2.0
specification
defines a
new
High-speed
transfer
rate of
480
Mb/sec.
That is a
40X
increase
from the
1.1
specification
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More info
on USB
specification
at USB.ORG
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Frequently
Asked
Questions
on USB
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