<s>
Universal	B-Protocol
Serial	I-Protocol
Bus	I-Protocol
(	O
USB	B-Protocol
)	O
is	O
an	O
industry	O
standard	O
that	O
establishes	O
specifications	O
for	O
cables	O
,	O
connectors	O
and	O
protocols	O
for	O
connection	O
,	O
communication	O
and	O
power	O
supply	O
(	O
interfacing	B-Application
)	O
between	O
computers	O
,	O
peripherals	O
and	O
other	O
computers	O
.	O
</s>
<s>
A	O
broad	O
variety	O
of	O
USB	B-Protocol
hardware	O
exists	O
,	O
including	O
14	O
different	O
connector	O
types	O
,	O
of	O
which	O
USB-C	O
is	O
the	O
most	O
recent	O
and	O
the	O
only	O
one	O
not	O
currently	O
deprecated	O
since	O
the	O
release	O
of	O
USB	B-Protocol
3.2	O
.	O
</s>
<s>
First	O
released	O
in	O
1996	O
,	O
the	O
USB	B-Protocol
standards	O
are	O
maintained	O
by	O
the	O
USB	B-Protocol
Implementers	O
Forum	O
(	O
USB-IF	O
)	O
.	O
</s>
<s>
The	O
four	O
generations	O
of	O
USB	B-Protocol
are	O
:	O
USB	B-Protocol
1.x	O
,	O
USB	B-Protocol
2.0	O
,	O
USB	B-Protocol
3.x	O
,	O
and	O
USB4	O
.	O
</s>
<s>
USB	B-Protocol
was	O
designed	O
to	O
standardize	O
the	O
connection	O
of	O
peripherals	O
to	O
personal	O
computers	O
,	O
both	O
to	O
communicate	O
with	O
and	O
to	O
supply	O
electric	O
power	O
.	O
</s>
<s>
It	O
has	O
largely	O
replaced	O
interfaces	B-Application
such	O
as	O
serial	B-Protocol
ports	I-Protocol
and	O
parallel	B-Device
ports	I-Device
and	O
has	O
become	O
commonplace	O
on	O
a	O
wide	O
range	O
of	O
devices	O
.	O
</s>
<s>
Examples	O
of	O
peripherals	O
that	O
are	O
connected	O
via	O
USB	B-Protocol
include	O
computer	B-Device
keyboards	I-Device
and	O
mice	B-Device
,	O
video	B-Application
cameras	O
,	O
printers	O
,	O
portable	O
media	O
players	O
,	O
mobile	O
(	O
portable	O
)	O
digital	O
telephones	O
,	O
disk	O
drives	O
,	O
and	O
network	O
adapters	O
.	O
</s>
<s>
USB	B-Protocol
connectors	O
have	O
been	O
increasingly	O
replacing	O
other	O
types	O
as	O
charging	O
cables	O
of	O
portable	O
devices	O
.	O
</s>
<s>
Each	O
USB	B-Protocol
connection	O
is	O
made	O
using	O
two	O
connectors	O
:	O
a	O
socket	O
(	O
or	O
receptacle	O
)	O
and	O
a	O
plug	O
.	O
</s>
<s>
The	O
Universal	B-Protocol
Serial	I-Protocol
Bus	I-Protocol
was	O
developed	O
to	O
simplify	O
and	O
improve	O
the	O
interface	O
between	O
personal	O
computers	O
and	O
peripheral	O
devices	O
,	O
such	O
as	O
cell	O
phones	O
,	O
computer	O
accessories	O
,	O
and	O
monitors	O
,	O
when	O
compared	O
with	O
previously	O
existing	O
standard	O
or	O
ad	O
hoc	O
proprietary	O
interfaces	B-Application
.	O
</s>
<s>
From	O
the	O
computer	O
user	O
's	O
perspective	O
,	O
the	O
USB	B-Protocol
interface	O
improves	O
ease	O
of	O
use	O
in	O
several	O
ways	O
:	O
</s>
<s>
The	O
USB	B-Protocol
interface	O
is	O
self-configuring	O
,	O
eliminating	O
the	O
need	O
for	O
the	O
user	O
to	O
adjust	O
the	O
device	O
's	O
settings	O
for	O
speed	O
or	O
data	O
format	O
,	O
or	O
configure	O
interrupts	B-Application
,	O
input/output	O
addresses	O
,	O
or	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
channels	O
.	O
</s>
<s>
USB	B-Protocol
connectors	O
are	O
standardized	O
at	O
the	O
host	O
,	O
so	O
any	O
peripheral	O
can	O
use	O
most	O
available	O
receptacles	O
.	O
</s>
<s>
USB	B-Protocol
takes	O
full	O
advantage	O
of	O
the	O
additional	O
processing	O
power	O
that	O
can	O
be	O
economically	O
put	O
into	O
peripheral	O
devices	O
so	O
that	O
they	O
can	O
manage	O
themselves	O
.	O
</s>
<s>
As	O
such	O
,	O
USB	B-Protocol
devices	I-Protocol
often	O
do	O
not	O
have	O
user-adjustable	O
interface	O
settings	O
.	O
</s>
<s>
The	O
USB	B-Protocol
interface	O
is	O
hot-swappable	B-Device
(	O
devices	O
can	O
be	O
exchanged	O
without	O
rebooting	O
the	O
host	O
computer	O
)	O
.	O
</s>
<s>
Small	O
devices	O
can	O
be	O
powered	O
directly	O
from	O
the	O
USB	B-Protocol
interface	O
,	O
eliminating	O
the	O
need	O
for	O
additional	O
power	O
supply	O
cables	O
.	O
</s>
<s>
Because	O
use	O
of	O
the	O
USB	B-Protocol
logo	O
is	O
only	O
permitted	O
after	O
compliance	O
testing	O
,	O
the	O
user	O
can	O
have	O
confidence	O
that	O
a	O
USB	B-Protocol
device	I-Protocol
will	O
work	O
as	O
expected	O
without	O
extensive	O
interaction	O
with	O
settings	O
and	O
configuration	O
.	O
</s>
<s>
The	O
USB	B-Protocol
interface	O
defines	O
protocols	O
for	O
recovery	O
from	O
common	O
errors	O
,	O
improving	O
reliability	O
over	O
previous	O
interfaces	B-Application
.	O
</s>
<s>
Installing	O
a	O
device	O
that	O
relies	O
on	O
the	O
USB	B-Protocol
standard	O
requires	O
minimal	O
operator	O
action	O
.	O
</s>
<s>
When	O
a	O
user	O
plugs	O
a	O
device	O
into	O
a	O
port	O
on	O
a	O
running	O
computer	O
,	O
it	O
either	O
entirely	O
automatically	O
configures	O
using	O
existing	O
device	B-Application
drivers	I-Application
,	O
or	O
the	O
system	O
prompts	O
the	O
user	O
to	O
locate	O
a	O
driver	O
,	O
which	O
it	O
then	O
installs	O
and	O
configures	O
automatically	O
.	O
</s>
<s>
The	O
USB	B-Protocol
standard	O
also	O
provides	O
multiple	O
benefits	O
for	O
hardware	O
manufacturers	O
and	O
software	O
developers	O
,	O
specifically	O
in	O
the	O
relative	O
ease	O
of	O
implementation	O
:	O
</s>
<s>
The	O
USB	B-Protocol
standard	O
eliminates	O
the	O
requirement	O
to	O
develop	O
proprietary	O
interfaces	B-Application
to	O
new	O
peripherals	O
.	O
</s>
<s>
The	O
wide	O
range	O
of	O
transfer	O
speeds	O
available	O
from	O
a	O
USB	B-Protocol
interface	O
suits	O
devices	O
ranging	O
from	O
keyboards	B-Device
and	O
mice	B-Device
up	O
to	O
streaming	O
video	B-Application
interfaces	B-Application
.	O
</s>
<s>
A	O
USB	B-Protocol
interface	O
can	O
be	O
designed	O
to	O
provide	O
the	O
best	O
available	O
latency	O
for	O
time-critical	O
functions	O
or	O
can	O
be	O
set	O
up	O
to	O
do	O
background	O
transfers	O
of	O
bulk	O
data	O
with	O
little	O
impact	O
on	O
system	O
resources	O
.	O
</s>
<s>
The	O
USB	B-Protocol
interface	O
is	O
generalized	O
with	O
no	O
signal	O
lines	O
dedicated	O
to	O
only	O
one	O
function	O
of	O
one	O
device	O
.	O
</s>
<s>
As	O
with	O
all	O
standards	O
,	O
USB	B-Protocol
possesses	O
multiple	O
limitations	O
to	O
its	O
design	O
:	O
</s>
<s>
USB	B-Protocol
cables	O
are	O
limited	O
in	O
length	O
,	O
as	O
the	O
standard	O
was	O
intended	O
for	O
peripherals	O
on	O
the	O
same	O
table-top	O
,	O
not	O
between	O
rooms	O
or	O
buildings	O
.	O
</s>
<s>
However	O
,	O
a	O
USB	B-Protocol
port	I-Protocol
can	O
be	O
connected	O
to	O
a	O
gateway	B-Application
that	O
accesses	O
distant	O
devices	O
.	O
</s>
<s>
USB	B-Protocol
data	O
transfer	O
rates	O
are	O
slower	O
than	O
those	O
of	O
other	O
interconnects	B-General_Concept
such	O
as	O
100	B-Protocol
Gigabit	I-Protocol
Ethernet	I-Protocol
.	O
</s>
<s>
USB	B-Protocol
has	O
a	O
strict	O
tree	B-Data_Structure
network	I-Data_Structure
topology	O
and	O
master/slave	B-Operating_System
protocol	O
for	O
addressing	O
peripheral	O
devices	O
;	O
those	O
devices	O
cannot	O
interact	O
with	O
one	O
another	O
except	O
via	O
the	O
host	O
,	O
and	O
two	O
hosts	O
cannot	O
communicate	O
over	O
their	O
USB	B-Protocol
ports	I-Protocol
directly	O
.	O
</s>
<s>
Some	O
extension	O
to	O
this	O
limitation	O
is	O
possible	O
through	O
USB	B-Protocol
On-The-Go	O
in	O
,	O
Dual-Role-Devices	O
and	O
protocol	O
bridge	O
.	O
</s>
<s>
While	O
converters	O
exist	O
between	O
certain	O
legacy	B-Device
interfaces	I-Device
and	O
USB	B-Protocol
,	O
they	O
might	O
not	O
provide	O
a	O
full	O
implementation	O
of	O
the	O
legacy	B-Device
hardware	I-Device
.	O
</s>
<s>
For	O
example	O
,	O
a	O
USB-to-parallel-port	O
converter	O
might	O
work	O
well	O
with	O
a	O
printer	O
,	O
but	O
not	O
with	O
a	O
scanner	B-Application
that	O
requires	O
bidirectional	O
use	O
of	O
the	O
data	O
pins	O
.	O
</s>
<s>
For	O
a	O
product	O
developer	O
,	O
using	O
USB	B-Protocol
requires	O
the	O
implementation	O
of	O
a	O
complex	O
protocol	O
and	O
implies	O
an	O
"	O
intelligent	O
"	O
controller	O
in	O
the	O
peripheral	O
device	O
.	O
</s>
<s>
Developers	O
of	O
USB	B-Protocol
devices	I-Protocol
intended	O
for	O
public	O
sale	O
generally	O
must	O
obtain	O
a	O
USB	B-Protocol
ID	O
,	O
which	O
requires	O
that	O
they	O
pay	O
a	O
fee	O
to	O
the	O
USB	B-Protocol
Implementers	O
Forum	O
(	O
USB-IF	O
)	O
.	O
</s>
<s>
Developers	O
of	O
products	O
that	O
use	O
the	O
USB	B-Protocol
specification	O
must	O
sign	O
an	O
agreement	O
with	O
the	O
USB-IF	O
.	O
</s>
<s>
Use	O
of	O
the	O
USB	B-Protocol
logos	O
on	O
the	O
product	O
requires	O
annual	O
fees	O
and	O
membership	O
in	O
the	O
organization	O
.	O
</s>
<s>
A	O
group	O
of	O
seven	O
companies	O
began	O
the	O
development	O
of	O
USB	B-Protocol
in	O
1995	O
:	O
Compaq	O
,	O
DEC	O
,	O
IBM	O
,	O
Intel	O
,	O
Microsoft	B-Application
,	O
NEC	O
,	O
and	O
Nortel	O
.	O
</s>
<s>
The	O
goal	O
was	O
to	O
make	O
it	O
fundamentally	O
easier	O
to	O
connect	O
external	O
devices	O
to	O
PCs	O
by	O
replacing	O
the	O
multitude	O
of	O
connectors	O
at	O
the	O
back	O
of	O
PCs	O
,	O
addressing	O
the	O
usability	O
issues	O
of	O
existing	O
interfaces	B-Application
,	O
and	O
simplifying	O
software	O
configuration	O
of	O
all	O
devices	O
connected	O
to	O
USB	B-Protocol
,	O
as	O
well	O
as	O
permitting	O
greater	O
data	O
transfer	O
rates	O
for	O
external	O
devices	O
and	O
Plug	B-Device
and	I-Device
Play	I-Device
features	O
.	O
</s>
<s>
Ajay	O
Bhatt	O
and	O
his	O
team	O
worked	O
on	O
the	O
standard	O
at	O
Intel	O
;	O
the	O
first	O
integrated	O
circuits	O
supporting	O
USB	B-Protocol
were	O
produced	O
by	O
Intel	O
in	O
1995	O
.	O
</s>
<s>
,	O
about	O
six	O
billion	O
USB	B-Protocol
ports	I-Protocol
and	O
interfaces	B-Application
were	O
in	O
the	O
global	O
marketplace	O
,	O
and	O
about	O
two	O
billion	O
were	O
being	O
sold	O
each	O
year	O
.	O
</s>
<s>
Few	O
USB	B-Protocol
devices	I-Protocol
made	O
it	O
to	O
the	O
market	O
until	O
USB1.1	O
was	O
released	O
in	O
August	O
1998	O
.	O
</s>
<s>
USB1.1	O
was	O
the	O
earliest	O
revision	O
that	O
was	O
widely	O
adopted	O
and	O
led	O
to	O
what	O
Microsoft	B-Application
designated	O
the	O
"	O
Legacy-free	B-Protocol
PC	I-Protocol
"	O
.	O
</s>
<s>
Neither	O
USB	B-Protocol
1.0	O
nor	O
1.1	O
specified	O
a	O
design	O
for	O
any	O
connector	O
smaller	O
than	O
the	O
standard	O
type	O
A	O
or	O
type	O
B	O
.	O
</s>
<s>
Modifications	O
to	O
the	O
USB	B-Protocol
specification	O
have	O
been	O
made	O
via	O
engineering	O
change	O
notices	O
(	O
ECNs	O
)	O
.	O
</s>
<s>
The	O
most	O
important	O
of	O
these	O
ECNs	O
are	O
included	O
into	O
the	O
USB2.0	O
specification	O
package	O
available	O
from	O
USB.org	O
:	O
</s>
<s>
The	O
USB3.0	O
specification	O
was	O
released	O
on	O
12	O
November	O
2008	O
,	O
with	O
its	O
management	O
transferring	O
from	O
USB3.0	O
Promoter	O
Group	O
to	O
the	O
USB	B-Protocol
Implementers	O
Forum	O
(	O
USB-IF	O
)	O
and	O
announced	O
on	O
17	O
November	O
2008	O
at	O
the	O
SuperSpeed	O
USB	B-Protocol
Developers	O
Conference	O
.	O
</s>
<s>
The	O
SuperSpeed	O
bus	B-General_Concept
provides	O
for	O
a	O
transfer	O
mode	O
at	O
a	O
nominal	O
rate	O
of	O
5.0Gbit/s	O
,	O
in	O
addition	O
to	O
the	O
three	O
existing	O
transfer	O
modes	O
.	O
</s>
<s>
Its	O
efficiency	O
is	O
dependent	O
on	O
a	O
number	O
of	O
factors	O
including	O
physical	O
symbol	O
encoding	B-Protocol
and	O
link	O
level	O
overhead	O
.	O
</s>
<s>
At	O
a	O
5Gbit/s	O
signaling	O
rate	O
with	O
8b/10b	B-Protocol
encoding	I-Protocol
,	O
each	O
byte	O
needs	O
10	O
bits	O
to	O
transmit	O
,	O
so	O
the	O
raw	O
throughput	O
is	O
500MB/s	O
.	O
</s>
<s>
When	O
flow	O
control	O
,	O
packet	B-Protocol
framing	O
and	O
protocol	O
overhead	O
are	O
considered	O
,	O
it	O
is	O
realistic	O
for	O
400MB/s	O
(	O
3.2Gbit/s	O
)	O
or	O
more	O
to	O
transmit	O
to	O
an	O
application	O
.	O
</s>
<s>
USB	B-Protocol
3.1	O
,	O
released	O
in	O
July	O
2013	O
has	O
two	O
variants	O
.	O
</s>
<s>
The	O
first	O
one	O
preserves	O
USB3.0	O
'	O
s	O
SuperSpeed	O
transfer	O
mode	O
and	O
is	O
labeled	O
USB	B-Protocol
3.1	O
Gen	O
1	O
,	O
and	O
the	O
second	O
version	O
introduces	O
a	O
new	O
SuperSpeed+	O
transfer	O
mode	O
under	O
the	O
label	O
of	O
USB	B-Protocol
3.1	O
Gen	O
2	O
.	O
</s>
<s>
SuperSpeed+	O
doubles	O
the	O
maximum	O
data	O
signaling	O
rate	O
to	O
10Gbit/s	O
,	O
while	O
reducing	O
line	B-Protocol
encoding	I-Protocol
overhead	O
to	O
just	O
3%	O
by	O
changing	O
the	O
encoding	B-Protocol
scheme	I-Protocol
to	O
128b/132b	O
.	O
</s>
<s>
USB	B-Protocol
3.2	O
,	O
released	O
in	O
September	O
2017	O
,	O
preserves	O
existing	O
USB3.1	O
SuperSpeed	O
and	O
SuperSpeed+	O
data	O
modes	O
but	O
introduces	O
two	O
new	O
SuperSpeed+	O
transfer	O
modes	O
over	O
the	O
new	O
USB-C	O
connector	O
with	O
data	O
rates	O
of	O
10	O
and	O
20Gbit/s	O
(	O
1.25	O
and	O
2.5GB/s	O
)	O
.	O
</s>
<s>
The	O
increase	O
in	O
bandwidth	O
is	O
a	O
result	O
of	O
multi-lane	O
operation	O
over	O
existing	O
wires	O
that	O
were	O
intended	O
for	O
flip-flop	O
capabilities	O
of	O
the	O
USB-C	O
connector	O
.	O
</s>
<s>
USB	B-Protocol
3.0	O
also	O
introduced	O
the	O
USB	B-Protocol
Attached	O
SCSI	O
protocol	O
(	O
UASP	O
)	O
,	O
which	O
provides	O
generally	O
faster	O
transfer	O
speeds	O
than	O
the	O
BOT	O
(	O
Bulk-Only-Transfer	O
)	O
protocol	O
.	O
</s>
<s>
Starting	O
with	O
the	O
USB	B-Protocol
3.2	O
standard	O
,	O
USB-IF	O
introduced	O
a	O
new	O
naming	O
scheme	O
.	O
</s>
<s>
To	O
help	O
companies	O
with	O
branding	O
of	O
the	O
different	O
transfer	O
modes	O
,	O
USB-IF	O
recommended	O
branding	O
the	O
5	O
,	O
10	O
,	O
and	O
20Gbit/s	O
transfer	O
modes	O
as	O
SuperSpeed	O
USB	B-Protocol
5Gbps	O
,	O
SuperSpeed	O
USB	B-Protocol
10Gbps	O
,	O
and	O
SuperSpeed	O
USB	B-Protocol
20Gbps	O
,	O
respectively	O
.	O
</s>
<s>
The	O
USB4	O
specification	O
was	O
released	O
on	O
29	O
August	O
2019	O
by	O
the	O
USB	B-Protocol
Implementers	O
Forum	O
.	O
</s>
<s>
USB4	O
is	O
based	O
on	O
the	O
Thunderbolt	B-Protocol
3	O
protocol	O
.	O
</s>
<s>
It	O
supports	O
40Gbit/s	O
throughput	O
,	O
is	O
compatible	O
with	O
Thunderbolt	B-Protocol
3	O
,	O
and	O
backward	O
compatible	O
with	O
USB3.2	O
and	O
USB2.0	O
.	O
</s>
<s>
Connection	O
Mandatory	O
for	O
Remarks	O
host	O
hub	O
device	O
USB	B-Protocol
2.0	O
(	O
480	O
Mbit/s	O
)	O
Contrary	O
to	O
other	O
functions	O
—	O
which	O
use	O
the	O
multiplexing	O
of	O
high-speed	O
links	O
—	O
USB	B-Protocol
2.0	O
over	O
USB-C	O
utilizes	O
its	O
own	O
differential	O
pair	O
of	O
wires	O
.	O
</s>
<s>
USB4	O
Gen	O
2×2	O
(	O
20	O
Gbit/s	O
)	O
A	O
USB	B-Protocol
3.0-labelled	O
device	O
still	O
operates	O
via	O
a	O
USB4	O
host	O
or	O
hub	O
as	O
a	O
USB	B-Protocol
3.0	O
device	O
.	O
</s>
<s>
USB4	O
Gen	O
3×2	O
(	O
40	O
Gbit/s	O
)	O
DisplayPort	B-Protocol
The	O
specification	O
requires	O
that	O
hosts	O
and	O
hubs	O
support	O
the	O
DisplayPort	B-Protocol
Alternate	O
Mode	O
.	O
</s>
<s>
PCI	B-Protocol
Express	O
The	O
PCI	B-Protocol
Express	O
function	O
of	O
USB4	O
replicates	O
the	O
functionality	O
of	O
previous	O
versions	O
of	O
the	O
Thunderbolt	B-Protocol
specification	O
.	O
</s>
<s>
Thunderbolt	B-Protocol
3	O
Thunderbolt	B-Protocol
3	O
uses	O
USB-C	O
cables	O
;	O
the	O
USB4	O
specification	O
allows	O
hosts	O
and	O
devices	O
and	O
requires	O
hubs	O
to	O
support	O
interoperability	O
with	O
the	O
standard	O
using	O
the	O
Thunderbolt	B-Protocol
3	O
Alternate	O
Mode	O
.	O
</s>
<s>
Other	O
Alternate	O
Modes	O
USB4	O
products	O
may	O
optionally	O
offer	O
interoperability	O
with	O
the	O
HDMI	B-Protocol
,	O
MHL	B-Protocol
,	O
and	O
VirtualLink	O
Alternate	O
Modes	O
.	O
</s>
<s>
During	O
CES	O
2020	O
,	O
USB-IF	O
and	O
Intel	O
stated	O
their	O
intention	O
to	O
allow	O
USB4	O
products	O
that	O
support	O
all	O
the	O
optional	O
functionality	O
as	O
Thunderbolt	B-Protocol
4	O
products	O
.	O
</s>
<s>
The	O
first	O
products	O
compatible	O
with	O
USB4	O
are	O
expected	O
to	O
be	O
Intel	O
's	O
Tiger	B-Device
Lake	I-Device
series	O
and	O
AMD	O
's	O
Zen	O
3	O
series	O
of	O
CPU	O
,	O
released	O
in	O
2020	O
.	O
</s>
<s>
The	O
USB4	O
2.0	O
specification	O
was	O
released	O
on	O
1	O
September	O
2022	O
by	O
the	O
USB	B-Protocol
Implementers	O
Forum	O
.	O
</s>
<s>
Because	O
of	O
the	O
previous	O
confusing	O
naming	O
schemes	O
,	O
USB-IF	O
decided	O
to	O
change	O
it	O
once	O
again	O
.	O
</s>
<s>
As	O
of	O
2	O
September	O
2022	O
,	O
marketing	O
names	O
follow	O
the	O
syntax	O
"	O
USB	B-Protocol
XGbps	O
"	O
,	O
where	O
X	O
is	O
the	O
speed	O
of	O
transfer	O
in	O
Gb/s	O
.	O
</s>
<s>
Full	O
Speed	O
(	O
12	O
Mbit/s	O
)	O
High	O
Speed	O
(	O
480	O
Mbit/s	O
)	O
SuperSpeed	O
USB	B-Protocol
(	O
5	O
Gbit/s	O
)	O
Also	O
referred	O
to	O
as	O
USB	B-Protocol
3.1	O
Gen	O
1	O
and	O
USB	B-Protocol
3.2	O
Gen	O
1	O
×	O
1	O
SuperSpeed+	O
USB	B-Protocol
(	O
10	O
Gbit/s	O
)	O
Includes	O
new	O
USB	B-Protocol
3.1	O
Gen	O
2	O
,	O
also	O
named	O
USB	B-Protocol
3.2	O
Gen	O
2	O
×	O
1	O
in	O
later	O
specifications	O
.	O
</s>
<s>
SuperSpeed+	O
USB	B-Protocol
dual-lane	O
(	O
20	O
Gbit/s	O
)	O
Includes	O
new	O
USB	B-Protocol
3.2	O
Gen	O
1	O
×	O
2	O
and	O
Gen	O
2	O
×	O
2	O
multi-link	O
modes	O
.	O
</s>
<s>
power	O
Note	O
USB	B-Protocol
Battery	O
Charging	O
Rev	O
.	O
</s>
<s>
1.0	O
2007-03-08	O
7.5	O
W	O
(	O
5	O
V	O
,	O
1.5	O
A	O
)	O
USB	B-Protocol
Battery	O
Charging	O
Rev	O
.	O
</s>
<s>
In	O
ordinary	O
USB	B-Protocol
2.0	O
'	O
s	O
standard-A	O
port	O
,	O
1.5	O
A	O
only	O
.	O
</s>
<s>
USB	B-Protocol
Battery	O
Charging	O
Rev	O
.	O
</s>
<s>
1.2	O
2010-12-07	O
7.5	O
W	O
(	O
5	O
V	O
,	O
1.5	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
1.0	O
(	O
V	O
.	O
1.0	O
)	O
2012-07-05	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
Using	O
FSK	O
protocol	O
over	O
bus	B-General_Concept
power	O
(	O
V	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
1.0	O
(	O
V	O
.	O
1.3	O
)	O
2014-03-11	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Type-C	O
Rev	O
.	O
</s>
<s>
1.0	O
2014-08-11	O
15	O
W	O
(	O
5	O
V	O
,	O
3	O
A	O
)	O
New	O
connector	O
and	O
cable	O
specification	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
2.0	O
(	O
V	O
.	O
1.0	O
)	O
2014-08-11	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
Using	O
BMC	O
protocol	O
over	O
communication	O
channel	O
(	O
CC	O
)	O
on	O
USB-C	O
cables	O
.	O
</s>
<s>
USB	B-Protocol
Type-C	O
Rev	O
.	O
</s>
<s>
1.1	O
2015-04-03	O
15	O
W	O
(	O
5	O
V	O
,	O
3	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
2.0	O
(	O
V	O
.	O
1.1	O
)	O
2015-05-07	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Type-C	O
Rev	O
.	O
</s>
<s>
1.2	O
2016-03-25	O
15	O
W	O
(	O
5	O
V	O
,	O
3	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
2.0	O
(	O
V	O
.	O
1.2	O
)	O
2016-03-25	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
2.0	O
(	O
V	O
.	O
1.3	O
)	O
2017-01-12	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
3.0	O
(	O
V	O
.	O
1.1	O
)	O
2017-01-12	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Type-C	O
Rev	O
.	O
</s>
<s>
1.3	O
2017-07-14	O
15	O
W	O
(	O
5	O
V	O
,	O
3	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
3.0	O
(	O
V	O
.	O
1.2	O
)	O
2018-06-21	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Type-C	O
Rev	O
.	O
</s>
<s>
1.4	O
2019-03-29	O
15	O
W	O
(	O
5	O
V	O
,	O
3	O
A	O
)	O
USB	B-Protocol
Type-C	O
Rev	O
.	O
</s>
<s>
2.0	O
2019-08-29	O
15	O
W	O
(	O
5	O
V	O
,	O
3	O
A	O
)	O
Enabling	O
USB4	O
over	O
USB	B-Protocol
Type-C	O
connectors	O
and	O
cables	O
.	O
</s>
<s>
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
3.0	O
(	O
V	O
.	O
2.0	O
)	O
2019-08-29	O
100	O
W	O
(	O
20	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
3.1	O
(	O
V	O
.	O
1.0	O
)	O
2021-05-24	O
240	O
W	O
(	O
48	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Type-C	O
Rev	O
.	O
</s>
<s>
2.1	O
2021-05-25	O
15	O
W	O
(	O
5	O
V	O
,	O
3	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
3.1	O
(	O
V	O
.	O
1.1	O
)	O
2021-07-06	O
240	O
W	O
(	O
48	O
V	O
,	O
5	O
A	O
)	O
USB	B-Protocol
Power	O
Delivery	O
Rev	O
.	O
</s>
<s>
A	O
USB	B-Protocol
system	O
consists	O
of	O
a	O
host	O
with	O
one	O
or	O
more	O
downstream	O
ports	O
,	O
and	O
multiple	O
peripherals	O
,	O
forming	O
a	O
tiered-star	B-Data_Structure
topology	O
.	O
</s>
<s>
Additional	O
USB	B-Protocol
hubs	O
may	O
be	O
included	O
,	O
allowing	O
up	O
to	O
five	O
tiers	O
.	O
</s>
<s>
A	O
USB	B-Protocol
host	O
may	O
have	O
multiple	O
controllers	O
,	O
each	O
with	O
one	O
or	O
more	O
ports	O
.	O
</s>
<s>
USB	B-Protocol
devices	I-Protocol
are	O
linked	O
in	O
series	O
through	O
hubs	O
.	O
</s>
<s>
A	O
USB	B-Protocol
device	I-Protocol
may	O
consist	O
of	O
several	O
logical	O
sub-devices	O
that	O
are	O
referred	O
to	O
as	O
device	O
functions	O
.	O
</s>
<s>
A	O
composite	O
device	O
may	O
provide	O
several	O
functions	O
,	O
for	O
example	O
,	O
a	O
webcam	B-Protocol
(	O
video	B-Application
device	O
function	O
)	O
with	O
a	O
built-in	O
microphone	B-Application
(	O
audio	O
device	O
function	O
)	O
.	O
</s>
<s>
An	O
alternative	O
to	O
this	O
is	O
a	O
compound	O
device	O
,	O
in	O
which	O
the	O
host	O
assigns	O
each	O
logical	O
device	O
a	O
distinct	O
address	O
and	O
all	O
logical	O
devices	O
connect	O
to	O
a	O
built-in	O
hub	O
that	O
connects	O
to	O
the	O
physical	O
USB	B-Protocol
cable	O
.	O
</s>
<s>
USB	B-Protocol
device	I-Protocol
communication	O
is	O
based	O
on	O
pipes	O
(	O
logical	O
channels	O
)	O
.	O
</s>
<s>
A	O
pipe	O
is	O
a	O
connection	O
from	O
the	O
host	O
controller	O
to	O
a	O
logical	O
entity	O
within	O
a	O
device	O
,	O
called	O
an	O
endpoint	B-Protocol
.	O
</s>
<s>
Each	O
USB	B-Protocol
device	I-Protocol
can	O
have	O
up	O
to	O
32	O
endpoints	O
(	O
16	O
in	O
and	O
16	O
out	O
)	O
,	O
though	O
it	O
is	O
rare	O
to	O
have	O
so	O
many	O
.	O
</s>
<s>
Message	O
pipes	O
are	O
typically	O
used	O
for	O
short	O
,	O
simple	O
commands	O
to	O
the	O
device	O
,	O
and	O
for	O
status	O
responses	O
from	O
the	O
device	O
,	O
used	O
,	O
for	O
example	O
,	O
by	O
the	O
bus	B-General_Concept
control	O
pipe	O
number	O
0	O
.	O
</s>
<s>
A	O
stream	O
pipe	O
is	O
a	O
uni-directional	O
pipe	O
connected	O
to	O
a	O
uni-directional	O
endpoint	B-Protocol
that	O
transfers	O
data	O
using	O
an	O
isochronous	O
,	O
interrupt	B-Application
,	O
or	O
bulk	O
transfer	O
:	O
</s>
<s>
When	O
a	O
host	O
starts	O
a	O
data	O
transfer	O
,	O
it	O
sends	O
a	O
TOKEN	O
packet	B-Protocol
containing	O
an	O
endpoint	B-Protocol
specified	O
with	O
a	O
tuple	B-Application
of	O
(	O
device_address	O
,	O
endpoint_number	O
)	O
.	O
</s>
<s>
If	O
the	O
transfer	O
is	O
from	O
the	O
host	O
to	O
the	O
endpoint	B-Protocol
,	O
the	O
host	O
sends	O
an	O
OUT	O
packet	B-Protocol
(	O
a	O
specialization	O
of	O
a	O
TOKEN	O
packet	B-Protocol
)	O
with	O
the	O
desired	O
device	O
address	O
and	O
endpoint	B-Protocol
number	O
.	O
</s>
<s>
If	O
the	O
data	O
transfer	O
is	O
from	O
the	O
device	O
to	O
the	O
host	O
,	O
the	O
host	O
sends	O
an	O
IN	O
packet	B-Protocol
instead	O
.	O
</s>
<s>
If	O
the	O
destination	O
endpoint	B-Protocol
is	O
a	O
uni-directional	O
endpoint	B-Protocol
whose	O
manufacturer	O
's	O
designated	O
direction	O
does	O
not	O
match	O
the	O
TOKEN	O
packet	B-Protocol
(	O
e.g.	O
</s>
<s>
the	O
manufacturer	O
's	O
designated	O
direction	O
is	O
IN	O
while	O
the	O
TOKEN	O
packet	B-Protocol
is	O
an	O
OUT	O
packet	B-Protocol
)	O
,	O
the	O
TOKEN	O
packet	B-Protocol
is	O
ignored	O
.	O
</s>
<s>
A	O
bi-directional	O
endpoint	B-Protocol
,	O
on	O
the	O
other	O
hand	O
,	O
accepts	O
both	O
IN	O
and	O
OUT	O
packets	B-Protocol
.	O
</s>
<s>
Endpoints	O
are	O
grouped	O
into	O
interfaces	B-Application
and	O
each	O
interface	O
is	O
associated	O
with	O
a	O
single	O
device	O
function	O
.	O
</s>
<s>
An	O
exception	O
to	O
this	O
is	O
endpoint	B-Protocol
zero	O
,	O
which	O
is	O
used	O
for	O
device	O
configuration	O
and	O
is	O
not	O
associated	O
with	O
any	O
interface	O
.	O
</s>
<s>
A	O
single	O
device	O
function	O
composed	O
of	O
independently	O
controlled	O
interfaces	B-Application
is	O
called	O
a	O
composite	O
device	O
.	O
</s>
<s>
When	O
a	O
USB	B-Protocol
device	I-Protocol
is	O
first	O
connected	O
to	O
a	O
USB	B-Protocol
host	O
,	O
the	O
USB	B-Protocol
device	I-Protocol
enumeration	O
process	O
is	O
started	O
.	O
</s>
<s>
The	O
enumeration	O
starts	O
by	O
sending	O
a	O
reset	O
signal	O
to	O
the	O
USB	B-Protocol
device	I-Protocol
.	O
</s>
<s>
The	O
data	O
rate	O
of	O
the	O
USB	B-Protocol
device	I-Protocol
is	O
determined	O
during	O
the	O
reset	O
signaling	O
.	O
</s>
<s>
After	O
reset	O
,	O
the	O
USB	B-Protocol
device	I-Protocol
's	O
information	O
is	O
read	O
by	O
the	O
host	O
and	O
the	O
device	O
is	O
assigned	O
a	O
unique	O
7-bit	O
address	O
.	O
</s>
<s>
If	O
the	O
device	O
is	O
supported	O
by	O
the	O
host	O
,	O
the	O
device	B-Application
drivers	I-Application
needed	O
for	O
communicating	O
with	O
the	O
device	O
are	O
loaded	O
and	O
the	O
device	O
is	O
set	O
to	O
a	O
configured	O
state	O
.	O
</s>
<s>
If	O
the	O
USB	B-Protocol
host	O
is	O
restarted	O
,	O
the	O
enumeration	O
process	O
is	O
repeated	O
for	O
all	O
connected	O
devices	O
.	O
</s>
<s>
The	O
host	O
controller	O
directs	O
traffic	O
flow	O
to	O
devices	O
,	O
so	O
no	O
USB	B-Protocol
device	I-Protocol
can	O
transfer	O
any	O
data	O
on	O
the	O
bus	B-General_Concept
without	O
an	O
explicit	O
request	O
from	O
the	O
host	O
controller	O
.	O
</s>
<s>
In	O
USB2.0	O
,	O
the	O
host	O
controller	O
polls	B-General_Concept
the	O
bus	B-General_Concept
for	O
traffic	O
,	O
usually	O
in	O
a	O
round-robin	B-Algorithm
fashion	O
.	O
</s>
<s>
The	O
throughput	O
of	O
each	O
USB	B-Protocol
port	I-Protocol
is	O
determined	O
by	O
the	O
slower	O
speed	O
of	O
either	O
the	O
USB	B-Protocol
port	I-Protocol
or	O
the	O
USB	B-Protocol
device	I-Protocol
connected	O
to	O
the	O
port	O
.	O
</s>
<s>
The	O
functionality	O
of	O
a	O
USB	B-Protocol
device	I-Protocol
is	O
defined	O
by	O
a	O
class	O
code	O
sent	O
to	O
a	O
USB	B-Protocol
host	O
.	O
</s>
<s>
Device	O
class	O
is	O
unspecified	O
,	O
interface	O
descriptors	O
are	O
used	O
to	O
determine	O
needed	O
drivers	O
01h	O
Interface	O
Audio	O
Speaker	O
,	O
microphone	B-Application
,	O
sound	B-Device
card	I-Device
,	O
MIDI	O
02h	O
Both	O
Communications	O
and	O
CDC	O
control	O
UART	O
and	O
RS-232	O
serial	B-Device
adapter	I-Device
,	O
Modem	B-Application
,	O
Wi-Fi	O
adapter	O
,	O
Ethernet	O
adapter	O
.	O
</s>
<s>
The	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
device	I-Architecture
class	I-Architecture
(	O
MSC	O
or	O
UMS	O
)	O
standardizes	O
connections	O
to	O
storage	O
devices	O
.	O
</s>
<s>
At	O
first	O
intended	O
for	O
magnetic	O
and	O
optical	O
drives	O
,	O
it	O
has	O
been	O
extended	O
to	O
support	O
flash	O
drives	O
and	O
SD	B-Device
card	I-Device
readers	O
.	O
</s>
<s>
The	O
ability	O
to	O
boot	O
a	O
write-locked	O
SD	B-Device
card	I-Device
with	O
a	O
USB	B-Device
adapter	I-Device
is	O
particularly	O
advantageous	O
for	O
maintaining	O
the	O
integrity	O
and	O
non-corruptible	O
,	O
pristine	O
state	O
of	O
the	O
booting	O
medium	O
.	O
</s>
<s>
Though	O
most	O
personal	O
computers	O
since	O
early	O
2005	O
can	O
boot	O
from	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
devices	I-Architecture
,	O
USB	B-Protocol
is	O
not	O
intended	O
as	O
a	O
primary	O
bus	B-General_Concept
for	O
a	O
computer	O
's	O
internal	O
storage	O
.	O
</s>
<s>
However	O
,	O
USB	B-Protocol
has	O
the	O
advantage	O
of	O
allowing	O
hot-swapping	B-Device
,	O
making	O
it	O
useful	O
for	O
mobile	O
peripherals	O
,	O
including	O
drives	O
of	O
various	O
kinds	O
.	O
</s>
<s>
Several	O
manufacturers	O
offer	O
external	O
portable	O
USB	B-Protocol
hard	B-Device
disk	I-Device
drives	I-Device
,	O
or	O
empty	O
enclosures	O
for	O
disk	O
drives	O
.	O
</s>
<s>
These	O
offer	O
performance	O
comparable	O
to	O
internal	O
drives	O
,	O
limited	O
by	O
the	O
number	O
and	O
types	O
of	O
attached	O
USB	B-Protocol
devices	I-Protocol
,	O
and	O
by	O
the	O
upper	O
limit	O
of	O
the	O
USB	B-Protocol
interface	O
.	O
</s>
<s>
Other	O
competing	O
standards	O
for	O
external	O
drive	O
connectivity	O
include	O
eSATA	O
,	O
ExpressCard	B-Device
,	O
FireWire	B-Protocol
(	O
IEEE	B-Protocol
1394	I-Protocol
)	O
,	O
and	O
most	O
recently	O
Thunderbolt	B-Protocol
.	O
</s>
<s>
Another	O
use	O
for	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
devices	I-Architecture
is	O
the	O
portable	O
execution	O
of	O
software	O
applications	O
(	O
such	O
as	O
web	O
browsers	O
and	O
VoIP	B-Application
clients	O
)	O
with	O
no	O
need	O
to	O
install	O
them	O
on	O
the	O
host	O
computer	O
.	O
</s>
<s>
Media	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
MTP	B-Protocol
)	O
was	O
designed	O
by	O
Microsoft	B-Application
to	O
give	O
higher-level	O
access	O
to	O
a	O
device	O
's	O
filesystem	O
than	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
,	O
at	O
the	O
level	O
of	O
files	O
rather	O
than	O
disk	O
blocks	O
.	O
</s>
<s>
MTP	B-Protocol
was	O
designed	O
for	O
use	O
with	O
portable	O
media	O
players	O
,	O
but	O
it	O
has	O
since	O
been	O
adopted	O
as	O
the	O
primary	O
storage	O
access	O
protocol	O
of	O
the	O
Android	B-Application
operating	I-Application
system	I-Application
from	O
the	O
version	O
4.1	O
Jelly	O
Bean	O
as	O
well	O
as	O
Windows	O
Phone	O
8	O
(	O
Windows	O
Phone	O
7	O
devices	O
had	O
used	O
the	O
Zune	O
protocol	O
an	O
evolution	O
of	O
MTP	B-Protocol
)	O
.	O
</s>
<s>
The	O
primary	O
reason	O
for	O
this	O
is	O
that	O
MTP	B-Protocol
does	O
not	O
require	O
exclusive	O
access	O
to	O
the	O
storage	O
device	O
the	O
way	O
UMS	O
does	O
,	O
alleviating	O
potential	O
problems	O
should	O
an	O
Android	B-Application
program	O
request	O
the	O
storage	O
while	O
it	O
is	O
attached	O
to	O
a	O
computer	O
.	O
</s>
<s>
The	O
main	O
drawback	O
is	O
that	O
MTP	B-Protocol
is	O
not	O
as	O
well	O
supported	O
outside	O
of	O
Windows	B-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
USB	B-Protocol
mice	B-Device
and	O
keyboards	B-Device
can	O
usually	O
be	O
used	O
with	O
older	O
computers	O
that	O
have	O
PS/2	B-Protocol
connectors	I-Protocol
with	O
the	O
aid	O
of	O
a	O
small	O
USB-to-PS/2	O
adapter	O
.	O
</s>
<s>
For	O
mice	B-Device
and	O
keyboards	B-Device
with	O
dual-protocol	O
support	O
,	O
an	O
adaptor	O
that	O
contains	O
no	O
logic	O
circuitry	O
may	O
be	O
used	O
:	O
the	O
USB	B-Protocol
hardware	O
in	O
the	O
keyboard	B-Device
or	O
mouse	B-Device
is	O
designed	O
to	O
detect	O
whether	O
it	O
is	O
connected	O
to	O
a	O
USB	B-Protocol
or	O
PS/2	B-Protocol
port	I-Protocol
,	O
and	O
communicate	O
using	O
the	O
appropriate	O
protocol	O
.	O
</s>
<s>
Converters	O
that	O
connect	O
PS/2	B-Protocol
keyboards	I-Protocol
and	O
mice	B-Device
(	O
usually	O
one	O
of	O
each	O
)	O
to	O
a	O
USB	B-Protocol
port	I-Protocol
also	O
exist	O
.	O
</s>
<s>
These	O
devices	O
present	O
two	O
HID	O
endpoints	O
to	O
the	O
system	O
and	O
use	O
a	O
microcontroller	B-Architecture
to	O
perform	O
bidirectional	O
data	O
translation	O
between	O
the	O
two	O
standards	O
.	O
</s>
<s>
Device	O
Firmware	B-Application
Upgrade	O
(	O
DFU	O
)	O
is	O
a	O
vendor	O
-	O
and	O
device-independent	O
mechanism	O
for	O
upgrading	O
the	O
firmware	B-Application
of	O
USB	B-Protocol
devices	I-Protocol
with	O
improved	O
versions	O
provided	O
by	O
their	O
manufacturers	O
,	O
offering	O
(	O
for	O
example	O
)	O
a	O
way	O
to	O
deploy	O
firmware	B-Application
bug	O
fixes	O
.	O
</s>
<s>
During	O
the	O
firmware	B-Application
upgrade	O
operation	O
,	O
USB	B-Protocol
devices	I-Protocol
change	O
their	O
operating	O
mode	O
effectively	O
becoming	O
a	O
PROM	B-General_Concept
programmer	O
.	O
</s>
<s>
Any	O
class	O
of	O
USB	B-Protocol
device	I-Protocol
can	O
implement	O
this	O
capability	O
by	O
following	O
the	O
official	O
DFU	O
specifications	O
.	O
</s>
<s>
DFU	O
can	O
also	O
give	O
the	O
user	O
the	O
freedom	O
to	O
flash	O
USB	B-Protocol
devices	I-Protocol
with	O
alternative	O
firmware	B-Application
.	O
</s>
<s>
One	O
consequence	O
of	O
this	O
is	O
that	O
USB	B-Protocol
devices	I-Protocol
after	O
being	O
re-flashed	O
may	O
act	O
as	O
various	O
unexpected	O
device	O
types	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
USB	B-Protocol
device	I-Protocol
that	O
the	O
seller	O
intends	O
to	O
be	O
just	O
a	O
flash	O
drive	O
can	O
"	O
spoof	O
"	O
an	O
input	O
device	O
like	O
a	O
keyboard	B-Device
.	O
</s>
<s>
The	O
USB	B-Protocol
Device	I-Protocol
Working	O
Group	O
has	O
laid	O
out	O
specifications	O
for	O
audio	O
streaming	O
,	O
and	O
specific	O
standards	O
have	O
been	O
developed	O
and	O
implemented	O
for	O
audio	O
class	O
uses	O
,	O
such	O
as	O
microphones	B-Application
,	O
speakers	O
,	O
headsets	O
,	O
telephones	O
,	O
musical	O
instruments	O
,	O
etc	O
.	O
</s>
<s>
The	O
working	O
group	O
has	O
published	O
three	O
versions	O
of	O
audio	O
device	O
specifications	O
:	O
USB	B-Protocol
Audio1.0	O
,	O
2.0	O
,	O
and	O
3.0	O
,	O
referred	O
to	O
as	O
"	O
UAC	O
"	O
or	O
"	O
ADC	O
"	O
.	O
</s>
<s>
UAC	O
2.0	O
introduced	O
support	O
for	O
High	O
Speed	O
USB	B-Protocol
(	O
in	O
addition	O
to	O
Full	O
Speed	O
)	O
,	O
allowing	O
greater	O
bandwidth	O
for	O
multi-channel	O
interfaces	B-Application
,	O
higher	O
sample	O
rates	O
,	O
lower	O
inherent	O
latency	O
,	O
and	O
8×	O
improvement	O
in	O
timing	O
resolution	O
in	O
synchronous	O
and	O
adaptive	O
modes	O
.	O
</s>
<s>
UAC	O
1.0	O
devices	O
are	O
still	O
common	O
,	O
however	O
,	O
due	O
to	O
their	O
cross-platform	O
driverless	O
compatibility	O
,	O
and	O
also	O
partly	O
due	O
to	O
Microsoft	B-Application
's	O
failure	O
to	O
implement	O
UAC	O
2.0	O
for	O
over	O
a	O
decade	O
after	O
its	O
publication	O
,	O
having	O
finally	O
added	O
support	O
to	O
Windows	B-Operating_System
10	I-Operating_System
through	O
the	O
Creators	O
Update	O
on	O
20	O
March	O
2017	O
.	O
</s>
<s>
UAC	O
2.0	O
is	O
also	O
supported	O
by	O
macOS	B-Application
,	O
iOS	B-Application
,	O
and	O
Linux	B-Application
,	O
however	O
Android	B-Application
only	O
implements	O
a	O
subset	O
of	O
the	O
UAC	O
1.0	O
specification	O
.	O
</s>
<s>
USB	B-Protocol
provides	O
three	O
isochronous	O
(	O
fixed-bandwidth	O
)	O
synchronization	O
types	O
,	O
all	O
of	O
which	O
are	O
used	O
by	O
audio	O
devices	O
:	O
</s>
<s>
Synchronous	O
The	O
device	O
's	O
clock	O
is	O
synced	O
to	O
the	O
USB	B-Protocol
start-of-frame	O
(	O
SOF	O
)	O
or	O
Bus	B-General_Concept
Interval	O
signals	O
.	O
</s>
<s>
While	O
the	O
USB	B-Protocol
spec	O
originally	O
described	O
asynchronous	O
mode	O
being	O
used	O
in	O
"	O
low	O
cost	O
speakers	O
"	O
and	O
adaptive	O
mode	O
in	O
"	O
high-end	O
digital	O
speakers	O
"	O
,	O
the	O
opposite	O
perception	O
exists	O
in	O
the	O
hi-fi	O
world	O
,	O
where	O
asynchronous	O
mode	O
is	O
advertised	O
as	O
a	O
feature	O
,	O
and	O
adaptive/synchronous	O
modes	O
have	O
a	O
bad	O
reputation	O
.	O
</s>
<s>
The	O
connectors	O
the	O
USB	B-Protocol
committee	O
specifies	O
support	O
a	O
number	O
of	O
USB	B-Protocol
's	O
underlying	O
goals	O
,	O
and	O
reflect	O
lessons	O
learned	O
from	O
the	O
many	O
connectors	O
the	O
computer	O
industry	O
has	O
used	O
.	O
</s>
<s>
The	O
official	O
USB	B-Protocol
specification	O
documents	O
also	O
periodically	O
define	O
the	O
term	O
male	O
to	O
represent	O
the	O
plug	O
,	O
and	O
female	O
to	O
represent	O
the	O
receptacle	O
.	O
</s>
<s>
The	O
design	O
is	O
intended	O
to	O
make	O
it	O
difficult	O
to	O
insert	O
a	O
USB	B-Protocol
plug	O
into	O
its	O
receptacle	O
incorrectly	O
.	O
</s>
<s>
The	O
USB	B-Protocol
specification	O
requires	O
that	O
the	O
cable	O
plug	O
and	O
receptacle	O
be	O
marked	O
so	O
the	O
user	O
can	O
recognize	O
the	O
proper	O
orientation	O
.	O
</s>
<s>
The	O
USB-C	O
plug	O
however	O
is	O
reversible	O
.	O
</s>
<s>
USB	B-Protocol
cables	O
and	O
small	O
USB	B-Protocol
devices	I-Protocol
are	O
held	O
in	O
place	O
by	O
the	O
gripping	O
force	O
from	O
the	O
receptacle	O
,	O
with	O
no	O
screws	O
,	O
clips	O
,	O
or	O
thumb-turns	O
as	O
some	O
connectors	O
use	O
.	O
</s>
<s>
However	O
,	O
some	O
of	O
this	O
directed	O
topology	O
is	O
lost	O
with	O
the	O
advent	O
of	O
multi-purpose	O
USB	B-Protocol
connections	O
(	O
such	O
as	O
USB	B-Protocol
On-The-Go	O
in	O
smartphones	O
,	O
and	O
USB-powered	O
Wi-Fi	O
routers	O
)	O
,	O
which	O
require	O
A-to-A	O
,	O
B-to-B	O
,	O
and	O
sometimes	O
Y/splitter	O
cables	O
.	O
</s>
<s>
USB	B-Protocol
connector	O
types	O
multiplied	O
as	O
the	O
specification	O
progressed	O
.	O
</s>
<s>
The	O
original	O
USB	B-Protocol
specification	O
detailed	O
standard-A	O
and	O
standard-B	O
plugs	O
and	O
receptacles	O
.	O
</s>
<s>
Charging	O
docks	O
supply	O
power	O
and	O
do	O
not	O
include	O
a	O
host	O
device	O
or	O
data	O
pins	O
,	O
allowing	O
any	O
capable	O
USB	B-Protocol
device	I-Protocol
to	O
charge	O
or	O
operate	O
from	O
a	O
standard	O
USB	B-Protocol
cable	O
.	O
</s>
<s>
USB	B-Protocol
bridge	O
cables	O
,	O
or	O
data	O
transfer	O
cables	O
can	O
be	O
found	O
within	O
the	O
market	O
,	O
offering	O
direct	O
PC	O
to	O
PC	O
connections	O
.	O
</s>
<s>
The	O
USB	B-Protocol
bridge	O
cables	O
are	O
used	O
to	O
transfer	O
files	O
between	O
two	O
computers	O
via	O
their	O
USB	B-Protocol
ports	I-Protocol
.	O
</s>
<s>
Popularized	O
by	O
Microsoft	B-Application
as	O
Windows	O
Easy	O
Transfer	O
,	O
the	O
Microsoft	B-Application
utility	O
used	O
a	O
special	O
USB	B-Protocol
bridge	O
cable	O
to	O
transfer	O
personal	O
files	O
and	O
settings	O
from	O
a	O
computer	O
running	O
an	O
earlier	O
version	O
of	O
Windows	O
to	O
a	O
computer	O
running	O
a	O
newer	O
version	O
.	O
</s>
<s>
Many	O
USB	B-Protocol
bridge	O
/	O
data	O
transfer	O
cables	O
are	O
still	O
USB	B-Protocol
2.0	O
,	O
but	O
there	O
are	O
also	O
a	O
number	O
of	O
USB	B-Protocol
3.0	O
transfer	O
cables	O
.	O
</s>
<s>
Despite	O
USB	B-Protocol
3.0	O
being	O
10	O
times	O
faster	O
than	O
USB	B-Protocol
2.0	O
,	O
USB	B-Protocol
3.0	O
transfer	O
cables	O
are	O
only	O
2	O
-	O
3	O
times	O
faster	O
given	O
their	O
design	O
.	O
</s>
<s>
The	O
USB	B-Protocol
3.0	O
specification	O
introduced	O
an	O
A-to-A	O
cross-over	O
cable	O
without	O
power	O
for	O
connecting	O
two	O
PCs	O
.	O
</s>
<s>
USB	B-Protocol
bridge	O
cables	O
have	O
become	O
less	O
important	O
with	O
USB	B-Protocol
dual-role-device	O
capabilities	O
introduced	O
with	O
the	O
USB	B-Protocol
3.1	O
specification	O
.	O
</s>
<s>
Under	O
the	O
most	O
recent	O
specifications	O
,	O
USB	B-Protocol
supports	O
most	O
scenarios	O
connecting	O
systems	O
directly	O
with	O
a	O
Type-C	O
cable	O
.	O
</s>
<s>
Upstream	O
USB	B-Protocol
connectors	O
supply	O
power	O
at	O
a	O
nominal	O
5V	O
DC	O
via	O
the	O
V_BUS	O
pin	O
to	O
downstream	O
USB	B-Protocol
devices	I-Protocol
.	O
</s>
<s>
1	O
unit	O
load	O
is	O
100	O
mA	O
for	O
USB	B-Protocol
devices	I-Protocol
up	O
to	O
USB2.0	O
,	O
while	O
USB3.0	O
defines	O
a	O
unit	O
load	O
as	O
150mA	O
.	O
</s>
<s>
High-power	O
devices	O
(	O
such	O
as	O
a	O
typical	O
2.5-inch	O
USB	B-Protocol
hard	B-Device
disk	I-Device
drive	I-Device
)	O
draw	O
at	O
least	O
1	O
unit	O
load	O
and	O
at	O
most	O
5-unit	O
loads	O
(	O
5x100mA	O
=	O
500mA	O
)	O
for	O
devices	O
up	O
to	O
USB2.0	O
-	O
or	O
6-unit	O
loads	O
(	O
6x150mA	O
=	O
900mA	O
)	O
for	O
SuperSpeed	O
(	O
USB	B-Protocol
3.0	O
and	O
up	O
)	O
devices	O
.	O
</s>
<s>
+	O
USB	B-Protocol
power	O
standards	O
Specification	O
Current	O
Voltage	O
Power	O
(	O
max	O
.	O
)	O
</s>
<s>
In	O
addition	O
to	O
standard	O
USB	B-Protocol
,	O
there	O
is	O
a	O
proprietary	O
high-powered	O
system	O
known	O
as	O
PoweredUSB	O
,	O
developed	O
in	O
the	O
1990s	O
,	O
and	O
mainly	O
used	O
in	O
point-of-sale	O
terminals	O
such	O
as	O
cash	O
registers	O
.	O
</s>
<s>
USB	B-Protocol
signals	O
are	O
transmitted	O
using	O
differential	O
signaling	O
on	O
a	O
twisted-pair	O
data	O
wires	O
with	O
characteristic	O
impedance	O
.	O
</s>
<s>
USB	B-Protocol
2.0	O
and	O
earlier	O
specifications	O
define	O
a	O
single	O
pair	O
in	O
half-duplex	O
(	O
HDx	O
)	O
.	O
</s>
<s>
USB	B-Protocol
3.0	O
and	O
later	O
specifications	O
define	O
one	O
pair	O
for	O
USB	B-Protocol
2.0	O
compatibility	O
and	O
two	O
or	O
four	O
pairs	O
for	O
data	O
transfer	O
:	O
two	O
pairs	O
in	O
full-duplex	O
(	O
FDx	O
)	O
for	O
single	O
lane	O
variants	O
(	O
requires	O
SuperSpeed	O
connectors	O
)	O
;	O
four	O
pairs	O
in	O
full-duplex	O
for	O
dual	O
lane	O
( ×2	O
)	O
variants	O
(	O
requires	O
USB-C	O
connector	O
)	O
.	O
</s>
<s>
SuperSpeed+	O
(	O
SS+	O
)	O
uses	O
increased	O
data	O
rate	O
(	O
Gen	O
2×1	O
mode	O
)	O
and/or	O
the	O
additional	O
lane	O
in	O
the	O
USB-C	O
connector	O
(	O
Gen	O
1×2	O
and	O
Gen	O
2×2	O
mode	O
)	O
.	O
</s>
<s>
A	O
USB	B-Protocol
connection	O
is	O
always	O
between	O
a	O
host	O
or	O
hub	O
at	O
the	O
A	O
connector	O
end	O
,	O
and	O
a	O
device	O
or	O
hub	O
's	O
"	O
upstream	O
"	O
port	O
at	O
the	O
other	O
end	O
.	O
</s>
<s>
During	O
USB	B-Protocol
communication	O
,	O
data	O
is	O
transmitted	O
as	O
packets	B-Protocol
.	O
</s>
<s>
Initially	O
,	O
all	O
packets	B-Protocol
are	O
sent	O
from	O
the	O
host	O
via	O
the	O
root	O
hub	O
,	O
and	O
possibly	O
more	O
hubs	O
,	O
to	O
devices	O
.	O
</s>
<s>
Some	O
of	O
those	O
packets	B-Protocol
direct	O
a	O
device	O
to	O
send	O
some	O
packets	B-Protocol
in	O
reply	O
.	O
</s>
<s>
The	O
basic	O
transactions	O
of	O
USB	B-Protocol
are	O
:	O
</s>
<s>
The	O
USB	B-Protocol
Implementers	O
Forum	O
introduced	O
the	O
Media	O
Agnostic	O
USB	B-Protocol
(	O
MA-USB	O
)	O
v.1.0	O
wireless	O
communication	O
standard	O
based	O
on	O
the	O
USB	B-Protocol
protocol	I-Protocol
on	O
July	O
29	O
,	O
2015	O
.	O
</s>
<s>
Wireless	O
USB	B-Protocol
is	O
a	O
cable-replacement	O
technology	O
,	O
and	O
uses	O
ultra-wideband	O
wireless	O
technology	O
for	O
data	O
rates	O
of	O
up	O
to	O
480Mbit/s	O
.	O
</s>
<s>
The	O
USB-IF	O
used	O
WiGig	O
Serial	O
Extension	O
v1.2	O
specification	O
as	O
its	O
initial	O
foundation	O
for	O
the	O
MA-USB	O
specification	O
and	O
is	O
compliant	O
with	O
SuperSpeed	O
USB	B-Protocol
(	O
3.0	O
and	O
3.1	O
)	O
and	O
Hi-Speed	O
USB	B-Protocol
(	O
USB	B-Protocol
2.0	O
)	O
.	O
</s>
<s>
Devices	O
that	O
use	O
MA-USB	O
will	O
be	O
branded	O
as	O
'	O
Powered	O
by	O
MA-USB	O
'	O
,	O
provided	O
the	O
product	O
qualifies	O
its	O
certification	O
program	O
.	O
</s>
<s>
InterChip	B-Device
USB	I-Device
is	O
a	O
chip-to-chip	O
variant	O
that	O
eliminates	O
the	O
conventional	O
transceivers	O
found	O
in	O
normal	O
USB	B-Protocol
.	O
</s>
<s>
The	O
HSIC	O
physical	B-Application
layer	I-Application
uses	O
about	O
50%	O
less	O
power	O
and	O
75%	O
less	O
board	O
area	O
compared	O
to	O
USB2.0	O
.	O
</s>
<s>
It	O
is	O
an	O
alternative	O
standard	O
to	O
SPI	B-Architecture
and	O
I2C	O
.	O
</s>
<s>
USB-C	O
(	O
officially	O
USB	B-Protocol
Type-C	O
)	O
is	O
a	O
standard	O
that	O
defines	O
a	O
new	O
connector	O
,	O
and	O
several	O
new	O
connection	O
features	O
.	O
</s>
<s>
Among	O
them	O
it	O
supports	O
Alternate	O
Mode	O
,	O
which	O
allows	O
transporting	O
other	O
protocols	O
via	O
the	O
USB-C	O
connector	O
and	O
cable	O
.	O
</s>
<s>
This	O
is	O
commonly	O
used	O
to	O
support	O
the	O
DisplayPort	B-Protocol
or	O
HDMI	B-Protocol
protocols	O
,	O
which	O
allows	O
connecting	O
a	O
display	O
,	O
such	O
as	O
a	O
computer	B-Device
monitor	I-Device
or	O
television	O
set	O
,	O
via	O
USB-C	O
.	O
</s>
<s>
All	O
other	O
connectors	O
were	O
deprecated	O
in	O
USB	B-Protocol
3.2	O
.	O
</s>
<s>
DisplayLink	O
is	O
a	O
technology	O
which	O
allows	O
multiple	O
displays	O
to	O
be	O
connected	O
to	O
a	O
computer	O
via	O
USB	B-Protocol
.	O
</s>
<s>
It	O
was	O
introduced	O
around	O
2006	O
,	O
and	O
before	O
the	O
advent	O
of	O
Alternate	O
Mode	O
over	O
USB-C	O
it	O
was	O
the	O
only	O
way	O
to	O
connect	O
displays	O
via	O
USB	B-Protocol
.	O
</s>
<s>
It	O
is	O
a	O
proprietary	O
technology	O
,	O
not	O
standardized	O
by	O
the	O
USB	B-Protocol
Implementers	O
Forum	O
and	O
typically	O
requires	O
a	O
separate	O
device	B-Application
driver	I-Application
on	O
the	O
computer	O
.	O
</s>
<s>
At	O
first	O
,	O
USB	B-Protocol
was	O
considered	O
a	O
complement	O
to	O
IEEE	B-Protocol
1394	I-Protocol
(	O
FireWire	B-Protocol
)	O
technology	O
,	O
which	O
was	O
designed	O
as	O
a	O
high-bandwidth	O
serial	O
bus	B-General_Concept
that	O
efficiently	O
interconnects	B-General_Concept
peripherals	O
such	O
as	O
disk	O
drives	O
,	O
audio	O
interfaces	B-Application
,	O
and	O
video	B-Application
equipment	O
.	O
</s>
<s>
In	O
the	O
initial	O
design	O
,	O
USB	B-Protocol
operated	O
at	O
a	O
far	O
lower	O
data	O
rate	O
and	O
used	O
less	O
sophisticated	O
hardware	O
.	O
</s>
<s>
It	O
was	O
suitable	O
for	O
small	O
peripherals	O
such	O
as	O
keyboards	B-Device
and	O
pointing	O
devices	O
.	O
</s>
<s>
The	O
most	O
significant	O
technical	O
differences	O
between	O
FireWire	B-Protocol
and	O
USB	B-Protocol
include	O
:	O
</s>
<s>
USB	B-Protocol
networks	O
use	O
a	O
tiered-star	B-Data_Structure
topology	O
,	O
while	O
IEEE1394	B-Protocol
networks	O
use	O
a	O
tree	B-Data_Structure
topology	I-Data_Structure
.	O
</s>
<s>
A	O
FireWire	B-Protocol
device	O
can	O
communicate	O
with	O
any	O
other	O
node	O
at	O
any	O
time	O
,	O
subject	O
to	O
network	O
conditions	O
.	O
</s>
<s>
A	O
USB	B-Protocol
network	O
relies	O
on	O
a	O
single	O
host	O
at	O
the	O
top	O
of	O
the	O
tree	B-Data_Structure
to	O
control	O
the	O
network	O
.	O
</s>
<s>
In	O
a	O
FireWire	B-Protocol
network	O
,	O
any	O
capable	O
node	O
can	O
control	O
the	O
network	O
.	O
</s>
<s>
USB	B-Protocol
runs	O
with	O
a	O
5V	O
power	O
line	O
,	O
while	O
FireWire	B-Protocol
supplies	O
12V	O
and	O
theoretically	O
can	O
supply	O
up	O
to	O
30V	O
.	O
</s>
<s>
Standard	O
USB	B-Protocol
hub	O
ports	O
can	O
provide	O
from	O
the	O
typical	O
500mA/2.5W	O
of	O
current	O
,	O
only	O
100mA	O
from	O
non-hub	O
ports	O
.	O
</s>
<s>
USB3.0	O
and	O
USB	B-Protocol
On-The-Go	O
supply	O
1.8A/9.0W	O
(	O
for	O
dedicated	O
battery	O
charging	O
,	O
1.5A/7.5W	O
full	O
bandwidth	O
or	O
900mA/4.5W	O
high	O
bandwidth	O
)	O
,	O
while	O
FireWire	B-Protocol
can	O
in	O
theory	O
supply	O
up	O
to	O
60watts	O
of	O
power	O
,	O
although	O
10	O
to	O
20watts	O
is	O
more	O
typical	O
.	O
</s>
<s>
These	O
and	O
other	O
differences	O
reflect	O
the	O
differing	O
design	O
goals	O
of	O
the	O
two	O
buses	O
:	O
USB	B-Protocol
was	O
designed	O
for	O
simplicity	O
and	O
low	O
cost	O
,	O
while	O
FireWire	B-Protocol
was	O
designed	O
for	O
high	O
performance	O
,	O
particularly	O
in	O
time-sensitive	O
applications	O
such	O
as	O
audio	O
and	O
video	B-Application
.	O
</s>
<s>
Although	O
similar	O
in	O
theoretical	O
maximum	O
transfer	O
rate	O
,	O
FireWire400	O
is	O
faster	O
than	O
USB2.0	O
high-bandwidth	O
in	O
real-use	O
,	O
especially	O
in	O
high-bandwidth	O
use	O
such	O
as	O
external	O
hard	B-Device
drives	I-Device
.	O
</s>
<s>
The	O
newer	O
FireWire800	B-Protocol
standard	O
is	O
twice	O
as	O
fast	O
as	O
FireWire400	O
and	O
faster	O
than	O
USB2.0	O
high-bandwidth	O
both	O
theoretically	O
and	O
practically	O
.	O
</s>
<s>
However	O
,	O
FireWire	B-Protocol
's	O
speed	O
advantages	O
rely	O
on	O
low-level	O
techniques	O
such	O
as	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
(	O
DMA	O
)	O
,	O
which	O
in	O
turn	O
have	O
created	O
opportunities	O
for	O
security	O
exploits	O
such	O
as	O
the	O
DMA	O
attack	O
.	O
</s>
<s>
The	O
chipset	O
and	O
drivers	O
used	O
to	O
implement	O
USB	B-Protocol
and	O
FireWire	B-Protocol
have	O
a	O
crucial	O
impact	O
on	O
how	O
much	O
of	O
the	O
bandwidth	O
prescribed	O
by	O
the	O
specification	O
is	O
achieved	O
in	O
the	O
real	O
world	O
,	O
along	O
with	O
compatibility	O
with	O
peripherals	O
.	O
</s>
<s>
The	O
IEEE	B-Device
802.3af	I-Device
,	O
802.3at	B-Device
,	O
and	O
802.3bt	O
Power	B-Device
over	I-Device
Ethernet	I-Device
(	O
PoE	B-Device
)	O
standards	O
specify	O
more	O
elaborate	O
power	O
negotiation	O
schemes	O
than	O
powered	O
USB	B-Protocol
.	O
</s>
<s>
They	O
operate	O
at	O
48VDC	O
and	O
can	O
supply	O
more	O
power	O
(	O
up	O
to	O
12.95W	O
for	O
802.3af	B-Device
,	O
25.5W	O
for	O
802.3at	B-Device
aka	O
PoE+	B-Device
,	O
71W	O
for	O
802.3bt	O
aka	O
4PPoE	B-Device
)	O
over	O
a	O
cable	O
up	O
to	O
100meters	O
compared	O
to	O
USB2.0	O
,	O
which	O
provides	O
2.5W	O
with	O
a	O
maximum	O
cable	O
length	O
of	O
5meters	O
.	O
</s>
<s>
This	O
has	O
made	O
PoE	B-Device
popular	O
for	O
VoIP	B-Application
telephones	O
,	O
security	O
cameras	O
,	O
wireless	B-Device
access	I-Device
points	I-Device
,	O
and	O
other	O
networked	O
devices	O
within	O
buildings	O
.	O
</s>
<s>
However	O
,	O
USB	B-Protocol
is	O
cheaper	O
than	O
PoE	B-Device
provided	O
that	O
the	O
distance	O
is	O
short	O
and	O
power	O
demand	O
is	O
low	O
.	O
</s>
<s>
USB	B-Protocol
has	O
no	O
such	O
requirement	O
as	O
it	O
was	O
designed	O
for	O
peripherals	O
closely	O
associated	O
with	O
a	O
host	O
computer	O
,	O
and	O
in	O
fact	O
it	O
connects	O
the	O
peripheral	O
and	O
host	O
grounds	O
.	O
</s>
<s>
This	O
gives	O
Ethernet	O
a	O
significant	O
safety	O
advantage	O
over	O
USB	B-Protocol
with	O
peripherals	O
such	O
as	O
cable	O
and	O
DSL	O
modems	B-Application
connected	O
to	O
external	O
wiring	O
that	O
can	O
assume	O
hazardous	O
voltages	O
under	O
certain	O
fault	O
conditions	O
.	O
</s>
<s>
The	O
USB	B-Protocol
Device	I-Protocol
Class	O
Definition	O
for	O
MIDI	O
Devices	O
transmits	O
Music	O
Instrument	O
Digital	O
Interface	O
(	O
MIDI	O
)	O
music	O
data	O
over	O
USB	B-Protocol
.	O
</s>
<s>
USB	B-Protocol
is	O
competitive	O
for	O
low-cost	O
and	O
physically	O
adjacent	O
devices	O
.	O
</s>
<s>
However	O
,	O
Power	B-Device
over	I-Device
Ethernet	I-Device
and	O
the	O
MIDI	O
plug	O
standard	O
have	O
an	O
advantage	O
in	O
high-end	O
devices	O
that	O
may	O
have	O
long	O
cables	O
.	O
</s>
<s>
USB	B-Protocol
can	O
cause	O
ground	O
loop	O
problems	O
between	O
equipment	O
,	O
because	O
it	O
connects	O
ground	O
references	O
on	O
both	O
transceivers	O
.	O
</s>
<s>
The	O
eSATA	O
connector	O
is	O
a	O
more	O
robust	O
SATA	O
connector	O
,	O
intended	O
for	O
connection	O
to	O
external	O
hard	B-Device
drives	I-Device
and	O
SSDs	B-Device
.	O
</s>
<s>
This	O
is	O
an	O
increasing	O
disadvantage	O
compared	O
to	O
USB	B-Protocol
.	O
</s>
<s>
Even	O
though	O
USB3.0	O
'	O
s	O
4.5W	O
is	O
sometimes	O
insufficient	O
to	O
power	O
external	O
hard	B-Device
drives	I-Device
,	O
technology	O
is	O
advancing	O
,	O
and	O
external	O
drives	O
gradually	O
need	O
less	O
power	O
,	O
diminishing	O
the	O
eSATA	O
advantage	O
.	O
</s>
<s>
eSATAp	O
(	O
power	O
over	O
eSATA	O
;	O
aka	O
ESATA/USB	O
)	O
is	O
a	O
connector	O
introduced	O
in	O
2009	O
that	O
supplies	O
power	O
to	O
attached	O
devices	O
using	O
a	O
new	O
,	O
backward	O
compatible	O
,	O
connector	O
.	O
</s>
<s>
On	O
a	O
notebook	O
eSATAp	O
usually	O
supplies	O
only	O
5V	O
to	O
power	O
a	O
2.5-inch	O
HDD/SSD	O
;	O
on	O
a	O
desktop	O
workstation	O
it	O
can	O
additionally	O
supply	O
12V	O
to	O
power	O
larger	O
devices	O
including	O
3.5-inch	O
HDD/SSD	O
and	O
5.25-inch	O
optical	O
drives	O
.	O
</s>
<s>
eSATAp	O
support	O
can	O
be	O
added	O
to	O
a	O
desktop	O
machine	O
in	O
the	O
form	O
of	O
a	O
bracket	O
connecting	O
the	O
motherboard	O
SATA	O
,	O
power	O
,	O
and	O
USB	B-Protocol
resources	O
.	O
</s>
<s>
eSATA	O
,	O
like	O
USB	B-Protocol
,	O
supports	O
hot	B-Device
plugging	I-Device
,	O
although	O
this	O
might	O
be	O
limited	O
by	O
OS	O
drivers	O
and	O
device	O
firmware	B-Application
.	O
</s>
<s>
Thunderbolt	B-Protocol
combines	O
PCI	B-Protocol
Express	O
and	O
Mini	B-Protocol
DisplayPort	I-Protocol
into	O
a	O
new	O
serial	O
data	O
interface	O
.	O
</s>
<s>
Original	O
Thunderbolt	B-Protocol
implementations	O
have	O
two	O
channels	O
,	O
each	O
with	O
a	O
transfer	O
speed	O
of	O
10Gbit/s	O
,	O
resulting	O
in	O
an	O
aggregate	O
unidirectional	O
bandwidth	O
of	O
20Gbit/s	O
.	O
</s>
<s>
Thunderbolt	B-Protocol
2	O
uses	O
link	O
aggregation	O
to	O
combine	O
the	O
two	O
10Gbit/s	O
channels	O
into	O
one	O
bidirectional	O
20Gbit/s	O
channel	O
.	O
</s>
<s>
Thunderbolt	B-Protocol
3	O
uses	O
the	O
USB-C	O
connector	O
.	O
</s>
<s>
Thunderbolt	B-Protocol
3	O
controllers	O
can	O
incorporate	O
a	O
USB3.1	O
Gen	O
2	O
controller	O
to	O
provide	O
compatibility	O
with	O
USB	B-Protocol
devices	I-Protocol
.	O
</s>
<s>
They	O
are	O
also	O
capable	O
of	O
providing	O
DisplayPort	B-Protocol
alternate	O
mode	O
over	O
the	O
USB-C	O
connector	O
,	O
making	O
a	O
Thunderbolt3	O
port	O
a	O
superset	O
of	O
a	O
USB3.1	O
Gen	O
2	O
port	O
with	O
DisplayPort	B-Protocol
alternate	O
mode	O
.	O
</s>
<s>
DisplayPort	B-Protocol
Alt	O
Mode	O
2.0	O
:	O
USB	B-Protocol
4	O
supports	O
DisplayPort	B-Protocol
2.0	O
over	O
its	O
alternative	O
mode	O
.	O
</s>
<s>
DisplayPort	B-Protocol
2.0	O
can	O
support	O
8K	O
resolution	O
at	O
60Hz	O
with	O
HDR10	O
color	O
.	O
</s>
<s>
DisplayPort	B-Protocol
2.0	O
can	O
use	O
up	O
to	O
80	O
Gbit/s	O
,	O
which	O
is	O
double	O
the	O
amount	O
available	O
to	O
USB	B-Protocol
data	O
,	O
because	O
it	O
sends	O
all	O
the	O
data	O
in	O
one	O
direction	O
(	O
to	O
the	O
monitor	O
)	O
and	O
can	O
thus	O
use	O
all	O
eight	O
data	O
lanes	O
at	O
once	O
.	O
</s>
<s>
After	O
the	O
specification	O
was	O
made	O
royalty-free	O
and	O
custodianship	O
of	O
the	O
Thunderbolt	B-Protocol
protocol	O
was	O
transferred	O
from	O
Intel	O
to	O
the	O
USB	B-Protocol
Implementers	O
Forum	O
,	O
Thunderbolt	B-Protocol
3	O
has	O
been	O
effectively	O
implemented	O
in	O
the	O
USB4	O
specification	O
—	O
with	O
compatibility	O
with	O
Thunderbolt	B-Protocol
3	O
optional	O
but	O
encouraged	O
for	O
USB4	O
products	O
.	O
</s>
<s>
Various	O
protocol	O
converters	O
are	O
available	O
that	O
convert	O
USB	B-Protocol
data	O
signals	O
to	O
and	O
from	O
other	O
communications	O
standards	O
.	O
</s>
<s>
Due	O
to	O
the	O
prevalency	O
of	O
the	O
USB	B-Protocol
standard	O
,	O
there	O
are	O
many	O
exploits	O
using	O
the	O
USB	B-Protocol
standard	O
.	O
</s>
<s>
One	O
of	O
the	O
biggest	O
instances	O
of	O
this	O
today	O
is	O
known	O
as	O
the	O
USB	B-Protocol
Killer	O
,	O
a	O
device	O
which	O
damages	O
devices	O
by	O
sending	O
high	O
voltage	O
pulses	O
across	O
the	O
data	O
lines	O
.	O
</s>
<s>
In	O
versions	O
of	O
Microsoft	B-Application
Windows	I-Application
before	O
Windows	B-Application
XP	I-Application
,	O
Windows	O
would	O
automatically	O
run	O
a	O
script	O
(	O
if	O
present	O
)	O
on	O
certain	O
devices	O
via	O
autorun	O
,	O
one	O
of	O
which	O
are	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
devices	I-Architecture
,	O
which	O
may	O
contain	O
malicious	O
software	O
.	O
</s>
