<s>
Secure	B-Device
Digital	I-Device
,	O
officially	O
abbreviated	O
as	O
SD	B-Device
,	O
is	O
a	O
proprietary	B-Device
non-volatile	B-General_Concept
flash	B-Device
memory	I-Device
card	I-Device
format	O
developed	O
by	O
the	O
SD	B-Device
Association	O
(	O
SDA	O
)	O
for	O
use	O
in	O
portable	O
devices	O
.	O
</s>
<s>
The	O
three	O
companies	O
formed	O
SD-3C	O
,	O
LLC	O
,	O
a	O
company	O
that	O
licenses	O
and	O
enforces	O
intellectual	O
property	O
rights	O
associated	O
with	O
SD	B-Device
memory	I-Device
cards	I-Device
and	O
SD	B-Device
host	O
and	O
ancillary	O
products	O
.	O
</s>
<s>
The	O
companies	O
also	O
formed	O
the	O
SD	B-Device
Association	O
(	O
SDA	O
)	O
,	O
a	O
non-profit	O
organization	O
,	O
in	O
January	O
2000	O
to	O
promote	O
and	O
create	O
SD	B-Device
Card	I-Device
standards	O
.	O
</s>
<s>
The	O
SDA	O
uses	O
several	O
trademarked	O
logos	B-Device
owned	O
and	O
licensed	O
by	O
SD-3C	O
to	O
enforce	O
compliance	O
with	O
its	O
specifications	O
and	O
assure	O
users	O
of	O
compatibility	O
.	O
</s>
<s>
In	O
1999	O
,	O
SanDisk	O
,	O
Panasonic	O
(	O
Matsushita	O
)	O
,	O
and	O
Toshiba	O
agreed	O
to	O
develop	O
and	O
market	O
the	O
Secure	B-Device
Digital	I-Device
(	O
SD	B-Device
)	O
Memory	B-Device
Card	I-Device
.	O
</s>
<s>
The	O
card	O
was	O
derived	O
from	O
the	O
MultiMediaCard	O
(	O
MMC	O
)	O
and	O
provided	O
digital	O
rights	O
management	O
based	O
on	O
the	O
Secure	B-Device
Digital	I-Device
Music	O
Initiative	O
(	O
SDMI	O
)	O
standard	O
and	O
for	O
the	O
time	O
,	O
a	O
high	O
memory	O
density	O
.	O
</s>
<s>
The	O
trademarked	O
"	O
SD	B-Device
"	O
logo	B-Device
was	O
originally	O
developed	O
for	O
the	O
Super	O
Density	O
Disc	O
,	O
which	O
was	O
the	O
unsuccessful	O
Toshiba	O
entry	O
in	O
the	O
DVD	O
format	O
war	O
.	O
</s>
<s>
For	O
this	O
reason	O
the	O
D	O
within	O
the	O
logo	B-Device
resembles	O
an	O
optical	O
disc	O
.	O
</s>
<s>
At	O
the	O
2000	O
Consumer	O
Electronics	O
Show	O
(	O
CES	O
)	O
trade	O
show	O
,	O
the	O
three	O
companies	O
announced	O
the	O
creation	O
of	O
the	O
SD	B-Device
Association	O
(	O
SDA	O
)	O
to	O
promote	O
SD	B-Device
cards	I-Device
.	O
</s>
<s>
The	O
SD	B-Device
Association	O
,	O
headquartered	O
in	O
San	O
Ramon	O
,	O
California	O
,	O
United	O
States	O
,	O
started	O
with	O
about	O
30	O
companies	O
and	O
today	O
consists	O
of	O
about	O
1,000	O
product	O
manufacturers	O
that	O
make	O
interoperable	O
memory	B-Device
cards	I-Device
and	O
devices	O
.	O
</s>
<s>
Early	O
samples	O
of	O
the	O
SD	B-Device
card	I-Device
became	O
available	O
in	O
the	O
first	O
quarter	O
of	O
2000	O
,	O
with	O
production	O
quantities	O
of	O
32	O
and	O
64	O
MB	O
cards	O
available	O
three	O
months	O
later	O
.	O
</s>
<s>
The	O
miniSD	B-Device
form	O
was	O
introduced	O
at	O
March	O
2003	O
CeBIT	O
by	O
SanDisk	O
Corporation	O
which	O
announced	O
and	O
demonstrated	O
it	O
.	O
</s>
<s>
The	O
SDA	O
adopted	O
the	O
miniSD	B-Device
card	O
in	O
2003	O
as	O
a	O
small	O
form	O
factor	O
extension	O
to	O
the	O
SD	B-Device
card	I-Device
standard	O
.	O
</s>
<s>
While	O
the	O
new	O
cards	O
were	O
designed	O
especially	O
for	O
mobile	O
phones	O
,	O
they	O
are	O
usually	O
packaged	O
with	O
a	O
miniSD	B-Device
adapter	O
that	O
provides	O
compatibility	O
with	O
a	O
standard	O
SD	B-Device
memory	I-Device
card	I-Device
slot	O
.	O
</s>
<s>
The	O
microSD	O
removable	O
miniaturized	O
Secure	B-Device
Digital	I-Device
flash	B-Device
memory	I-Device
cards	I-Device
were	O
originally	O
named	O
T-Flash	O
or	O
TF	O
,	O
abbreviations	O
of	O
TransFlash	O
.	O
</s>
<s>
microSD	O
(	O
and	O
TransFlash	O
)	O
cards	O
are	O
electrically	O
compatible	O
with	O
larger	O
SD	B-Device
cards	I-Device
and	O
can	O
be	O
used	O
in	O
devices	O
that	O
accept	O
SD	B-Device
cards	I-Device
with	O
the	O
help	O
of	O
a	O
passive	O
adapter	O
,	O
which	O
contains	O
no	O
electronic	O
components	O
,	O
only	O
metal	O
traces	O
connecting	O
the	O
two	O
sets	O
of	O
contacts	O
.	O
</s>
<s>
Unlike	O
the	O
larger	O
SD	B-Device
cards	I-Device
,	O
microSD	O
does	O
not	O
offer	O
a	O
mechanical	O
write	O
protect	O
switch	O
,	O
thus	O
an	O
operating-system-independent	O
way	O
of	O
write	O
protecting	O
them	O
does	O
not	O
exist	O
in	O
the	O
general	O
case	O
.	O
</s>
<s>
SanDisk	O
conceived	O
microSD	O
when	O
its	O
Chief	O
Technology	O
Officer	O
(	O
CTO	O
)	O
and	O
the	O
CTO	O
of	O
Motorola	O
concluded	O
that	O
current	O
memory	B-Device
cards	I-Device
were	O
too	O
large	O
for	O
mobile	O
phones	O
.	O
</s>
<s>
The	O
card	O
was	O
originally	O
called	O
T-Flash	O
,	O
but	O
just	O
before	O
product	O
launch	O
,	O
T-Mobile	O
sent	O
a	O
cease-and-desist	O
letter	O
to	O
SanDisk	O
claiming	O
that	O
T-Mobile	O
owned	O
the	O
trademark	O
on	O
T-(anything )	O
,	O
and	O
the	O
name	O
was	O
changed	O
to	O
TransFlash	O
.	O
</s>
<s>
At	O
CTIA	O
Wireless	O
2005	O
,	O
the	O
SDA	O
announced	O
the	O
small	O
microSD	O
form	O
factor	O
along	O
with	O
SDHC	O
secure	B-Device
digital	I-Device
high	O
capacity	O
formatting	O
in	O
excess	O
of	O
2	O
GB	O
with	O
a	O
minimum	O
sustained	O
read	O
and	O
write	O
speed	O
of	O
17.6Mbit/s	O
.	O
</s>
<s>
The	O
SDHC	O
format	O
,	O
announced	O
in	O
January	O
2006	O
,	O
brought	O
improvements	O
such	O
as	O
32	O
GB	O
storage	O
capacity	O
and	O
mandatory	O
support	O
for	O
FAT32	B-Application
file	B-Application
system	I-Application
.	O
</s>
<s>
In	O
April	O
,	O
the	O
SDA	O
released	O
a	O
detailed	O
specification	O
for	O
the	O
non-security	O
related	O
parts	O
of	O
the	O
SD	B-Device
memory	I-Device
card	I-Device
standard	O
and	O
for	O
the	O
Secure	B-Device
Digital	I-Device
Input	B-General_Concept
Output	I-General_Concept
(	O
SDIO	O
)	O
cards	O
and	O
the	O
standard	O
SD	B-Device
host	O
controller	O
.	O
</s>
<s>
Like	O
the	O
SD	B-Device
and	O
SDHC	O
,	O
the	O
miniSDHC	O
card	O
has	O
the	O
same	O
form	O
factor	O
as	O
the	O
older	O
miniSD	B-Device
card	O
but	O
the	O
HC	O
card	O
requires	O
HC	O
support	O
built	O
into	O
the	O
host	O
device	O
.	O
</s>
<s>
Devices	O
that	O
support	O
miniSDHC	O
work	O
with	O
miniSD	B-Device
and	O
miniSDHC	O
,	O
but	O
devices	O
without	O
specific	O
support	O
for	O
miniSDHC	O
work	O
only	O
with	O
the	O
older	O
miniSD	B-Device
card	O
.	O
</s>
<s>
Since	O
2008	O
,	O
miniSD	B-Device
cards	O
are	O
no	O
longer	O
produced	O
,	O
due	O
to	O
market	O
domination	O
of	O
the	O
even	O
smaller	O
microSD	O
cards	O
.	O
</s>
<s>
The	O
storage	O
density	O
of	O
memory	B-Device
cards	I-Device
has	O
increased	O
significantly	O
throughout	O
the	O
2010s	O
decade	O
,	O
allowing	O
the	O
earliest	O
devices	O
to	O
offer	O
support	O
for	O
the	O
SD:XC	O
standard	O
,	O
such	O
as	O
the	O
Samsung	B-Application
Galaxy	I-Application
S	I-Application
III	I-Application
and	O
Samsung	B-Operating_System
Galaxy	I-Operating_System
Note	I-Operating_System
II	I-Operating_System
mobile	O
phones	O
,	O
to	O
expand	O
their	O
available	O
storage	O
to	O
several	O
hundreds	O
of	O
gigabytes	O
.	O
</s>
<s>
SDXC	O
cards	O
are	O
formatted	O
with	O
the	O
exFAT	B-Application
filesystem	I-Application
by	O
default	O
.	O
</s>
<s>
But	O
only	O
early	O
in	O
2010	O
did	O
compatible	O
host	O
devices	O
come	O
onto	O
the	O
market	O
,	O
including	O
Sony	O
's	O
Handycam	B-Algorithm
HDR-CX55V	O
camcorder	O
,	O
Canon	O
's	O
EOS	B-Algorithm
550D	I-Algorithm
(	O
also	O
known	O
as	O
Rebel	B-Algorithm
T2i	I-Algorithm
)	O
Digital	B-Device
SLR	I-Device
camera	I-Device
,	O
a	O
USB	B-Protocol
card	O
reader	O
from	O
Panasonic	O
,	O
and	O
an	O
integrated	O
SDXC	O
card	O
reader	O
from	O
JMicron	O
.	O
</s>
<s>
The	O
earliest	O
laptops	B-Device
to	O
integrate	O
SDXC	O
card	O
readers	O
relied	O
on	O
a	O
USB	B-Protocol
2.0	O
bus	O
,	O
which	O
does	O
not	O
have	O
the	O
bandwidth	O
to	O
support	O
SDXC	O
at	O
full	O
speed	O
.	O
</s>
<s>
An	O
adapter	O
allows	O
MicroP2	O
cards	O
to	O
work	O
in	O
current	O
P2	B-Device
card	I-Device
equipment	O
.	O
</s>
<s>
Later	O
that	O
year	O
,	O
Lexar	O
released	O
the	O
first	O
256GB	O
SDXC	O
card	O
,	O
based	O
on	O
20nm	O
NAND	O
flash	B-Device
technology	O
.	O
</s>
<s>
Samsung	B-Application
announced	O
the	O
world	O
's	O
first	O
EVO	O
Plus	O
256GB	O
microSDXC	O
card	O
in	O
May	O
2016	O
,	O
and	O
in	O
September	O
2016	O
Western	O
Digital	O
(	O
SanDisk	O
)	O
announced	O
that	O
a	O
prototype	O
of	O
the	O
first	O
1	O
TB	O
SDXC	O
card	O
would	O
be	O
demonstrated	O
at	O
Photokina	O
.	O
</s>
<s>
The	O
Secure	B-Device
Digital	I-Device
Ultra	O
Capacity	O
(	O
SDUC	O
)	O
format	O
supports	O
cards	O
up	O
to	O
128	O
TB	O
and	O
offers	O
speeds	O
up	O
to	O
985	O
MB/s	O
.	O
</s>
<s>
Secure	B-Device
Digital	I-Device
includes	O
five	O
card	O
families	O
available	O
in	O
three	O
sizes	O
.	O
</s>
<s>
The	O
five	O
families	O
are	O
the	O
original	O
Standard-Capacity	O
(	O
SDSC	O
)	O
,	O
the	O
High-Capacity	O
(	O
SDHC	O
)	O
,	O
the	O
eXtended-Capacity	O
(	O
SDXC	O
)	O
,	O
the	O
Ultra-Capacity	O
(	O
SDUC	O
)	O
and	O
the	O
SDIO	O
,	O
which	O
combines	O
input/output	B-General_Concept
functions	O
with	O
data	B-General_Concept
storage	I-General_Concept
.	O
</s>
<s>
The	O
SD	B-Device
card	I-Device
's	O
small	O
footprint	O
is	O
an	O
ideal	O
storage	B-General_Concept
medium	I-General_Concept
for	O
smaller	O
,	O
thinner	O
,	O
and	O
more	O
portable	O
electronic	O
devices	O
.	O
</s>
<s>
The	O
second-generation	O
Secure	B-Device
Digital	I-Device
(	O
SDSC	O
or	O
Secure	B-Device
Digital	I-Device
Standard	O
Capacity	O
)	O
card	O
was	O
developed	O
to	O
improve	O
on	O
the	O
MultiMediaCard	O
(	O
MMC	O
)	O
standard	O
,	O
which	O
continued	O
to	O
evolve	O
,	O
but	O
in	O
a	O
different	O
direction	O
.	O
</s>
<s>
Secure	B-Device
Digital	I-Device
changed	O
the	O
MMC	O
design	O
in	O
several	O
ways	O
:	O
</s>
<s>
Asymmetrical	O
shape	O
of	O
the	O
sides	O
of	O
the	O
SD	B-Device
card	I-Device
prevent	O
inserting	O
it	O
upside	O
down	O
(	O
whereas	O
an	O
MMC	O
goes	O
in	O
most	O
of	O
the	O
way	O
but	O
makes	O
no	O
contact	O
if	O
inverted	O
)	O
.	O
</s>
<s>
Most	O
SD	B-Device
cards	I-Device
are	O
thick	O
,	O
compared	O
to	O
for	O
MMCs	O
.	O
</s>
<s>
The	O
SD	B-Device
specification	O
defines	O
a	O
card	O
called	O
Thin	O
SD	B-Device
with	O
a	O
thickness	O
of	O
1.4mm	O
,	O
but	O
they	O
occur	O
only	O
rarely	O
,	O
as	O
the	O
SDA	O
went	O
on	O
to	O
define	O
even	O
smaller	O
form	O
factors	O
.	O
</s>
<s>
The	O
SD	B-Device
specification	O
envisioned	O
capacities	O
and	O
transfer	O
rates	O
exceeding	O
those	O
of	O
MMC	O
,	O
and	O
both	O
of	O
these	O
functionalities	O
have	O
grown	O
over	O
time	O
.	O
</s>
<s>
While	O
MMC	O
uses	O
a	O
single	O
pin	O
for	O
data	O
transfers	O
,	O
the	O
SD	B-Device
card	I-Device
added	O
a	O
four-wire	O
bus	O
mode	O
for	O
higher	O
data	O
rates	O
.	O
</s>
<s>
The	O
SD	B-Device
card	I-Device
added	O
Content	O
Protection	O
for	O
Recordable	B-General_Concept
Media	I-General_Concept
(	O
CPRM	O
)	O
security	O
circuitry	O
for	O
digital	O
rights	O
management	O
(	O
DRM	O
)	O
content-protection	O
.	O
</s>
<s>
Full-size	O
SD	B-Device
cards	I-Device
do	O
not	O
fit	O
into	O
the	O
slimmer	O
MMC	O
slots	O
,	O
and	O
other	O
issues	O
also	O
affect	O
the	O
ability	O
to	O
use	O
one	O
format	O
in	O
a	O
host	O
device	O
designed	O
for	O
the	O
other	O
.	O
</s>
<s>
The	O
Secure	B-Device
Digital	I-Device
High	O
Capacity	O
(	O
SDHC	O
)	O
format	O
,	O
announced	O
in	O
January	O
2006	O
and	O
defined	O
in	O
version	O
2.0	O
of	O
the	O
SD	B-Device
specification	O
,	O
supports	O
cards	O
with	O
capacities	O
up	O
to	O
32GB	O
.	O
</s>
<s>
SDHC	O
cards	O
are	O
physically	O
and	O
electrically	O
identical	O
to	O
standard-capacity	O
SD	B-Device
cards	I-Device
(	O
SDSC	O
)	O
.	O
</s>
<s>
The	O
major	O
compatibility	O
issues	O
between	O
SDHC	O
and	O
SDSC	O
cards	O
are	O
the	O
redefinition	O
of	O
the	O
Card-Specific	O
Data	O
(	O
CSD	O
)	O
register	O
in	O
version	O
2.0	O
(	O
see	O
below	O
)	O
,	O
and	O
the	O
fact	O
that	O
SDHC	O
cards	O
are	O
shipped	O
preformatted	O
with	O
the	O
FAT32	B-Application
file	B-Application
system	I-Application
.	O
</s>
<s>
SDHC	O
host	O
devices	O
are	O
required	O
to	O
accept	O
older	O
SD	B-Device
cards	I-Device
.	O
</s>
<s>
However	O
,	O
older	O
host	O
devices	O
do	O
not	O
recognize	O
SDHC	O
or	O
SDXC	O
memory	B-Device
cards	I-Device
,	O
although	O
some	O
devices	O
can	O
do	O
so	O
through	O
a	O
firmware	O
upgrade	O
.	O
</s>
<s>
Older	O
Windows	B-Application
operating	I-Application
systems	I-Application
released	O
before	O
Windows	B-Application
7	O
require	O
patches	O
or	O
service	O
packs	O
to	O
support	O
access	O
to	O
SDHC	O
cards	O
.	O
</s>
<s>
The	O
Secure	B-Device
Digital	I-Device
eXtended	O
Capacity	O
(	O
SDXC	O
)	O
format	O
,	O
announced	O
in	O
January	O
2009	O
and	O
defined	O
in	O
version	O
3.01	O
of	O
the	O
SD	B-Device
specification	O
,	O
supports	O
cards	O
up	O
to	O
2TB	O
,	O
compared	O
to	O
a	O
limit	O
of	O
32GB	O
for	O
SDHC	O
cards	O
in	O
the	O
SD	B-Device
2.0	O
specification	O
.	O
</s>
<s>
SDXC	O
adopts	O
Microsoft	O
's	O
exFAT	B-Application
file	I-Application
system	I-Application
as	O
a	O
mandatory	O
feature	O
.	O
</s>
<s>
(	O
this	O
number	O
has	O
since	O
been	O
exceeded	O
with	O
SanDisk	O
proprietary	B-Device
technology	O
for	O
170MB/s	O
read	O
,	O
which	O
is	O
not	O
proprietary	B-Device
anymore	O
,	O
as	O
Lexar	O
has	O
the	O
1066x	O
running	O
at	O
160MB/s	O
read	O
and	O
120MB/s	O
write	O
via	O
UHS1	O
,	O
and	O
Kingston	O
also	O
has	O
their	O
Canvas	O
Go	O
!	O
</s>
<s>
Version	O
5.0	O
was	O
announced	O
in	O
February	O
2016	O
at	O
CP+	O
2016	O
,	O
and	O
added	O
"	O
Video	O
Speed	O
Class	O
"	O
ratings	O
for	O
UHS	O
cards	O
to	O
handle	O
higher	O
resolution	O
video	B-Application
formats	I-Application
like	O
8K	B-Architecture
.	O
</s>
<s>
The	O
Secure	B-Device
Digital	I-Device
Ultra	O
Capacity	O
(	O
SDUC	O
)	O
format	O
,	O
described	O
in	O
the	O
SD	B-Device
7.0	O
specification	O
,	O
and	O
announced	O
in	O
June	O
2018	O
,	O
supports	O
cards	O
up	O
to	O
128	O
TB	O
and	O
offers	O
speeds	O
up	O
to	O
985	O
MB/s	O
,	O
regardless	O
of	O
form	O
factor	O
,	O
either	O
micro	O
or	O
full	O
size	O
,	O
or	O
interface	O
type	O
including	O
UHS-I	O
,	O
UHS-II	O
,	O
UHS-III	O
or	O
SD	B-Device
Express	O
.	O
</s>
<s>
The	O
SD	B-Device
Express	O
interface	O
can	O
also	O
be	O
used	O
with	O
SDHC	O
and	O
SDXC	O
cards	O
.	O
</s>
<s>
SDXC	O
and	O
SDUC	O
cards	O
are	O
normally	O
formatted	O
using	O
the	O
exFAT	B-Application
file	I-Application
system	I-Application
,	O
thereby	O
limiting	O
their	O
use	O
to	O
a	O
limited	O
set	O
of	O
operating	O
systems	O
.	O
</s>
<s>
Therefore	O
,	O
exFAT-formatted	O
SDXC	O
cards	O
are	O
not	O
a	O
100%	O
universally	O
readable	O
exchange	O
medium	O
.	O
</s>
<s>
Windows	B-Application
Vista	I-Application
(	O
SP1	O
)	O
and	O
later	O
and	O
OS	B-Operating_System
X	I-Operating_System
(	O
10.6.5	O
and	O
later	O
)	O
have	O
native	O
support	O
for	O
exFAT	B-Application
.	O
</s>
<s>
(	O
Windows	B-Application
XP	O
and	O
Server	O
2003	O
can	O
support	O
exFAT	B-Application
via	O
an	O
optional	O
update	O
from	O
Microsoft	O
.	O
)	O
</s>
<s>
Most	O
BSD	B-Operating_System
and	O
Linux	B-Application
distributions	O
did	O
not	O
,	O
for	O
legal	O
reasons	O
;	O
though	O
in	O
Linux	B-Operating_System
kernel	I-Operating_System
5.4	O
Microsoft	O
open-sourced	O
the	O
spec	O
and	O
allowed	O
the	O
inclusion	O
of	O
an	O
exFAT	B-Application
driver	O
.	O
</s>
<s>
Users	O
of	O
older	O
kernels	B-Operating_System
or	O
BSD	B-Operating_System
can	O
manually	O
install	O
third-party	O
implementations	O
of	O
exFAT	B-Application
(	O
as	O
a	O
FUSE	B-Application
module	O
)	O
in	O
order	O
to	O
be	O
able	O
to	O
mount	O
exFAT-formatted	O
volumes	O
.	O
</s>
<s>
However	O
,	O
SDXC	O
cards	O
can	O
be	O
reformatted	O
to	O
use	O
any	O
file	B-Application
system	I-Application
(	O
such	O
as	O
ext4	B-Application
,	O
UFS	B-Operating_System
,	O
or	O
VFAT	B-Application
)	O
,	O
alleviating	O
the	O
restrictions	O
associated	O
with	O
exFAT	B-Application
availability	O
.	O
</s>
<s>
Except	O
for	O
the	O
change	O
of	O
file	B-Application
system	I-Application
,	O
SDXC	O
cards	O
are	O
mostly	O
backward	B-General_Concept
compatible	I-General_Concept
with	O
SDHC	O
readers	O
,	O
and	O
many	O
SDHC	O
host	O
devices	O
can	O
use	O
SDXC	O
cards	O
if	O
they	O
are	O
first	O
reformatted	O
to	O
the	O
FAT32	B-Application
file	B-Application
system	I-Application
.	O
</s>
<s>
Nevertheless	O
,	O
in	O
order	O
to	O
be	O
fully	O
compliant	O
with	O
the	O
SDXC	O
card	O
specification	O
,	O
some	O
SDXC-capable	O
host	O
devices	O
are	O
firmware-programmed	O
to	O
expect	O
exFAT	B-Application
on	O
cards	O
larger	O
than	O
32GB	O
.	O
</s>
<s>
Consequently	O
,	O
they	O
may	O
not	O
accept	O
SDXC	O
cards	O
reformatted	O
as	O
FAT32	B-Application
,	O
even	O
if	O
the	O
device	O
supports	O
FAT32	B-Application
on	O
smaller	O
cards	O
(	O
for	O
SDHC	O
compatibility	O
)	O
.	O
</s>
<s>
Therefore	O
,	O
even	O
if	O
a	O
file	B-Application
system	I-Application
is	O
supported	O
in	O
general	O
,	O
it	O
is	O
not	O
always	O
possible	O
to	O
use	O
alternative	O
file	B-Application
systems	I-Application
on	O
SDXC	O
cards	O
at	O
all	O
depending	O
on	O
how	O
strictly	O
the	O
SDXC	O
card	O
specification	O
has	O
been	O
implemented	O
in	O
the	O
host	O
device	O
.	O
</s>
<s>
This	O
bears	O
a	O
risk	O
of	O
accidental	O
loss	O
of	O
data	O
,	O
as	O
a	O
host	O
device	O
may	O
treat	O
a	O
card	O
with	O
an	O
unrecognized	O
file	B-Application
system	I-Application
as	O
blank	O
or	O
damaged	O
and	O
reformat	O
the	O
card	O
.	O
</s>
<s>
The	O
SD	B-Device
Association	O
provides	O
a	O
formatting	O
utility	O
for	O
Windows	B-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
that	O
checks	O
and	O
formats	O
SD	B-Device
,	O
SDHC	O
,	O
SDXC	O
,	O
and	O
SDUC	O
cards	O
.	O
</s>
<s>
SD	B-Device
card	I-Device
speed	O
is	O
customarily	O
rated	O
by	O
its	O
sequential	B-General_Concept
read	I-General_Concept
or	O
write	O
speed	O
.	O
</s>
<s>
The	O
sequential	O
performance	O
aspect	O
is	O
the	O
most	O
relevant	O
for	O
storing	O
and	O
retrieving	O
large	O
files	O
(	O
relative	O
to	O
block	B-General_Concept
sizes	I-General_Concept
internal	O
to	O
the	O
flash	B-Device
memory	I-Device
)	O
,	O
such	O
as	O
images	O
and	O
multimedia	O
.	O
</s>
<s>
Small	O
data	O
(	O
such	O
as	O
file	O
names	O
,	O
sizes	O
and	O
timestamps	O
)	O
falls	O
under	O
the	O
much	O
lower	O
speed	O
limit	O
of	O
random	B-General_Concept
access	I-General_Concept
,	O
which	O
can	O
be	O
the	O
limiting	O
factor	O
in	O
some	O
use	O
cases	O
.	O
</s>
<s>
With	O
early	O
SD	B-Device
cards	I-Device
,	O
a	O
few	O
card	O
manufacturers	O
specified	O
the	O
speed	O
as	O
a	O
"	O
times	O
"	O
("×"	O
)	O
rating	O
,	O
which	O
compared	O
the	O
average	O
speed	O
of	O
reading	O
data	O
to	O
that	O
of	O
the	O
original	O
CD-ROM	B-Device
drive	O
.	O
</s>
<s>
The	O
newer	O
families	O
of	O
SD	B-Device
card	I-Device
improve	O
card	O
speed	O
by	O
increasing	O
the	O
bus	O
rate	O
(	O
the	O
frequency	O
of	O
the	O
clock	O
signal	O
that	O
strobes	O
information	O
into	O
and	O
out	O
of	O
the	O
card	O
)	O
.	O
</s>
<s>
SD	B-Device
Cards	I-Device
will	O
read	O
and	O
write	O
at	O
speeds	O
of	O
12.5	O
MB/s	O
.	O
</s>
<s>
High	O
Speed	O
Mode	O
(	O
25	O
MB/s	O
)	O
was	O
introduced	O
to	O
support	O
digital	B-Device
cameras	I-Device
with	O
1.10	O
spec	O
version	O
.	O
</s>
<s>
Cards	O
that	O
comply	O
with	O
UHS	O
show	O
Roman	O
numerals	O
'	O
I	O
 '	O
,	O
'	O
II	O
 '	O
or	O
'	O
III	O
 '	O
next	O
to	O
the	O
SD	B-Device
card	I-Device
logo	B-Device
,	O
and	O
report	O
this	O
capability	O
to	O
the	O
host	O
device	O
.	O
</s>
<s>
Use	O
of	O
UHS-I	O
requires	O
that	O
the	O
host	O
device	O
command	O
the	O
card	O
to	O
drop	O
from	O
3.3-volt	O
to	O
1.8-volt	O
operation	O
over	O
the	O
I/O	B-General_Concept
interface	I-General_Concept
pins	O
and	O
select	O
the	O
four-bit	O
transfer	O
mode	O
,	O
while	O
UHS-II	O
requires	O
0.4-volt	O
operation	O
.	O
</s>
<s>
In	O
addition	O
to	O
enabling	O
higher	O
data	O
rates	O
,	O
the	O
UHS-II	O
interface	O
allows	O
for	O
lower	O
interface	O
power	O
consumption	O
,	O
lower	O
I/O	B-General_Concept
voltage	O
and	O
lower	O
electromagnetic	O
interference	O
(	O
EMI	O
)	O
.	O
</s>
<s>
Specified	O
in	O
SD	B-Device
version	O
3.01	O
.	O
</s>
<s>
There	O
is	O
a	O
proprietary	B-Device
UHS-I	O
extension	O
primarily	O
by	O
SanDisk	O
that	O
increases	O
transfer	O
speed	O
further	O
to	O
170MB/s	O
,	O
called	O
DDR208	O
(	O
or	O
DDR200	O
)	O
.	O
</s>
<s>
This	O
extension	O
has	O
since	O
then	O
been	O
used	O
by	O
Lexar	O
for	O
their	O
1066x	O
series	O
(	O
160MB/s	O
)	O
,	O
Kingston	O
Canvas	O
Go	O
Plus	O
(	O
170MB/s	O
)	O
and	O
the	O
MyMemory	O
PRO	O
SD	B-Device
card	I-Device
(	O
180MB/s	O
)	O
.	O
</s>
<s>
At	O
the	O
beginning	O
of	O
2021	O
,	O
there	O
were	O
more	O
than	O
50	O
DSLR	B-Device
and	O
compact	O
system	O
cameras	O
using	O
UHS-II	O
.	O
</s>
<s>
The	O
physical	O
interface	O
and	O
pin-layout	O
are	O
the	O
same	O
as	O
with	O
UHS-II	O
,	O
retaining	O
backward	B-General_Concept
compatibility	I-General_Concept
.	O
</s>
<s>
The	O
SD	B-Device
Express	O
bus	O
was	O
released	O
in	O
June	O
2018	O
with	O
SD	B-Device
specification	O
7.0	O
.	O
</s>
<s>
Supporting	O
cards	O
must	O
also	O
implement	O
the	O
NVM	B-Application
Express	I-Application
storage	O
access	O
protocol	O
.	O
</s>
<s>
For	O
legacy	O
application	O
use	O
,	O
SD	B-Device
Express	O
cards	O
must	O
also	O
support	O
High	O
Speed	O
bus	O
and	O
UHS-I	O
bus	O
.	O
</s>
<s>
Hosts	O
which	O
implement	O
version	O
7.0	O
of	O
the	O
spec	O
allow	O
SD	B-Device
Cards	I-Device
to	O
do	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
,	O
which	O
increases	O
the	O
attack	O
surface	O
of	O
the	O
host	O
dramatically	O
in	O
the	O
face	O
of	O
malicious	O
SD	B-Device
cards	I-Device
.	O
</s>
<s>
In	O
February	O
2019	O
,	O
the	O
SD	B-Device
Association	O
announced	O
microSD	O
Express	O
.	O
</s>
<s>
The	O
microSD	O
Express	O
cards	O
offer	O
PCI	O
Express	O
and	O
NVMe	B-Application
interfaces	O
,	O
as	O
the	O
June	O
2018	O
SD	B-Device
Express	O
release	O
did	O
,	O
alongside	O
the	O
legacy	O
microSD	O
interface	O
for	O
continued	O
backwards	B-General_Concept
compatibility	I-General_Concept
.	O
</s>
<s>
The	O
SDA	O
also	O
released	O
visual	O
marks	O
to	O
denote	O
microSD	O
Express	O
memory	B-Device
cards	I-Device
to	O
make	O
matching	O
the	O
card	O
and	O
device	O
easier	O
for	O
optimal	O
device	O
performance	O
.	O
</s>
<s>
The	O
SD	B-Device
Association	O
defines	O
standard	O
speed	O
classes	O
for	O
SDHC/SDXC	O
cards	O
indicating	O
minimum	O
performance	O
(	O
minimum	O
serial	O
data	O
writing	O
speed	O
)	O
.	O
</s>
<s>
The	O
SD	B-Device
Association	O
defines	O
three	O
types	O
of	O
Speed	O
Class	O
ratings	O
:	O
the	O
original	O
Speed	O
Class	O
,	O
UHS	O
Speed	O
Class	O
,	O
and	O
Video	O
Speed	O
Class	O
.	O
</s>
<s>
Class	O
10	O
asserts	O
that	O
the	O
card	O
supports	O
10MB/s	O
as	O
a	O
minimum	O
non-fragmented	O
sequential	B-General_Concept
write	I-General_Concept
speed	O
and	O
uses	O
a	O
High	O
Speed	O
bus	O
mode	O
.	O
</s>
<s>
UHS-I	O
and	O
UHS-II	O
cards	O
can	O
use	O
UHS	O
Speed	O
Class	O
rating	O
with	O
two	O
possible	O
grades	O
:	O
class	O
1	O
for	O
minimum	O
write	O
performance	O
of	O
at	O
least	O
10MB/s	O
( 	O
 '	O
U1	O
 '	O
symbol	O
featuring	O
number	O
1	O
inside	O
'	O
U	O
 '	O
)	O
and	O
class	O
3	O
for	O
minimum	O
write	O
performance	O
of	O
30MB/s	O
( 	O
 '	O
U3	O
 '	O
symbol	O
featuring	O
3	O
inside	O
'	O
U	O
 '	O
)	O
,	O
targeted	O
at	O
recording	O
4K	B-Architecture
video	I-Architecture
.	O
</s>
<s>
UHS	O
memory	B-Device
cards	I-Device
work	O
best	O
with	O
UHS	O
host	O
devices	O
.	O
</s>
<s>
The	O
combination	O
lets	O
the	O
user	O
record	O
HD	O
resolution	O
videos	B-Application
with	O
tapeless	B-Algorithm
camcorders	I-Algorithm
while	O
performing	O
other	O
functions	O
.	O
</s>
<s>
It	O
is	O
also	O
suitable	O
for	O
real-time	O
broadcasts	O
and	O
capturing	O
large	O
HD	O
videos	B-Application
.	O
</s>
<s>
Video	O
Speed	O
Class	O
defines	O
a	O
set	O
of	O
requirements	O
for	O
UHS	O
cards	O
to	O
match	O
the	O
modern	O
MLC	B-Device
NAND	I-Device
flash	I-Device
memory	O
and	O
supports	O
progressive	O
4K	B-Architecture
and	O
8K	B-Architecture
video	I-Architecture
with	O
minimum	O
sequential	O
writing	O
speeds	O
of	O
6	O
–	O
90MB/s	O
.	O
</s>
<s>
+	O
Comparison	O
of	O
SD	B-Device
card	I-Device
Speed	O
Class	O
ratings	O
Minimum	O
sequential	O
writing	O
speed	O
Speed	O
Class	O
Video	O
formatSuggested	O
max	O
.	O
</s>
<s>
Application	O
Performance	O
Class	O
is	O
a	O
newly	O
defined	O
standard	O
from	O
the	O
SD	B-Device
Specification	O
5.1	O
and	O
6.0	O
which	O
not	O
only	O
define	O
sequential	O
Writing	O
Speeds	O
but	O
also	O
mandates	O
a	O
minimum	O
IOPS	O
for	O
reading	O
and	O
writing	O
.	O
</s>
<s>
If	O
used	O
in	O
an	O
unsupported	O
host	O
,	O
they	O
might	O
even	O
be	O
slower	O
than	O
other	O
A1	O
cards	O
,	O
and	O
if	O
power	O
is	O
lost	O
before	O
cached	O
data	O
is	O
actually	O
written	O
from	O
the	O
card	O
's	O
internal	O
RAM	O
to	O
the	O
card	O
's	O
internal	O
flash	B-Device
RAM	I-Device
,	O
that	O
data	O
is	O
likely	O
to	O
be	O
lost	O
.	O
</s>
<s>
The	O
"	O
×	O
"	O
rating	O
,	O
that	O
was	O
used	O
by	O
some	O
card	O
manufacturers	O
and	O
made	O
obsolete	O
by	O
speed	O
classes	O
,	O
is	O
a	O
multiple	O
of	O
the	O
standard	O
CD-ROM	B-Device
drive	O
speed	O
of	O
150KB/s	O
(	O
approximately	O
1.23Mbit/s	O
)	O
.	O
</s>
<s>
Basic	O
cards	O
transfer	O
data	O
at	O
up	O
to	O
six	O
times	O
(	O
6×	O
)	O
the	O
CD-ROM	B-Device
speed	O
;	O
that	O
is	O
,	O
900kbit/s	O
or	O
7.37Mbit/s	O
.	O
</s>
<s>
In	O
applications	O
that	O
require	O
sustained	O
write	O
throughput	O
,	O
such	O
as	O
video	B-Application
recording	I-Application
,	O
the	O
device	O
might	O
not	O
perform	O
satisfactorily	O
if	O
the	O
SD	B-Device
card	I-Device
's	O
class	O
rating	O
falls	O
below	O
a	O
particular	O
speed	O
.	O
</s>
<s>
Digital	B-Device
cameras	I-Device
with	O
slow	O
cards	O
may	O
take	O
a	O
noticeable	O
time	O
after	O
taking	O
a	O
photograph	O
before	O
being	O
ready	O
for	O
the	O
next	O
,	O
while	O
the	O
camera	O
writes	O
the	O
first	O
picture	O
.	O
</s>
<s>
Write	B-Error_Name
amplification	I-Error_Name
:	O
The	O
flash	B-Device
controller	O
may	O
need	O
to	O
overwrite	O
more	O
data	O
than	O
requested	O
.	O
</s>
<s>
This	O
has	O
to	O
do	O
with	O
performing	O
read-modify-write	O
operations	O
on	O
write	O
blocks	O
,	O
freeing	O
up	O
(	O
the	O
much	O
larger	O
)	O
erase	O
blocks	O
,	O
while	O
moving	O
data	O
around	O
to	O
achieve	O
wear	B-Application
leveling	I-Application
.	O
</s>
<s>
File	B-Application
fragmentation	I-Application
:	O
where	O
there	O
is	O
not	O
sufficient	O
space	O
for	O
a	O
file	O
to	O
be	O
recorded	O
in	O
a	O
contiguous	O
region	O
,	O
it	O
is	O
split	O
into	O
non-contiguous	O
fragments	O
.	O
</s>
<s>
This	O
does	O
not	O
cause	O
rotational	O
or	O
head-movement	O
delays	O
as	O
with	O
electromechanical	O
hard	B-Device
drives	I-Device
,	O
but	O
may	O
decrease	O
speed⁠	O
⁠	O
⁠	O
—	O
for	O
instance	O
,	O
by	O
requiring	O
additional	O
reads	O
and	O
computation	O
to	O
determine	O
where	O
on	O
the	O
card	O
the	O
file	O
's	O
next	O
fragment	O
is	O
stored	O
.	O
</s>
<s>
In	O
addition	O
,	O
speed	O
may	O
vary	O
markedly	O
between	O
writing	O
a	O
large	O
amount	O
of	O
data	O
to	O
a	O
single	O
file	O
(	O
sequential	B-General_Concept
access	I-General_Concept
,	O
as	O
when	O
a	O
digital	B-Device
camera	I-Device
records	O
large	O
photographs	O
or	O
videos	B-Application
)	O
and	O
writing	O
a	O
large	O
number	O
of	O
small	O
files	O
(	O
a	O
random-access	B-General_Concept
use	O
common	O
in	O
smartphones	B-Application
)	O
.	O
</s>
<s>
A	O
study	O
in	O
2012	O
found	O
that	O
,	O
in	O
this	O
random-access	B-General_Concept
use	O
,	O
some	O
Class	O
2	O
cards	O
achieved	O
a	O
write	O
speed	O
of	O
1.38MB/s	O
,	O
while	O
all	O
cards	O
tested	O
of	O
Class	O
6	O
or	O
greater	O
(	O
and	O
some	O
of	O
lower	O
Classes	O
;	O
lower	O
Class	O
does	O
not	O
necessarily	O
mean	O
better	O
small-file	O
performance	O
)	O
,	O
including	O
those	O
from	O
major	O
manufacturers	O
,	O
were	O
over	O
100	O
times	O
slower	O
.	O
</s>
<s>
The	O
host	O
device	O
can	O
command	O
the	O
SD	B-Device
card	I-Device
to	O
become	O
read-only	O
(	O
to	O
reject	O
subsequent	O
commands	O
to	O
write	O
information	O
to	O
it	O
)	O
.	O
</s>
<s>
Most	O
full-size	O
SD	B-Device
cards	I-Device
have	O
a	O
"	O
mechanical	O
write	O
protect	O
switch	O
"	O
allowing	O
the	O
user	O
to	O
advise	O
the	O
host	O
computer	O
that	O
the	O
user	O
wants	O
the	O
device	O
to	O
be	O
treated	O
as	O
read-only	O
.	O
</s>
<s>
Some	O
host	O
devices	O
do	O
not	O
support	O
write	O
protection	O
,	O
which	O
is	O
an	O
optional	O
feature	O
of	O
the	O
SD	B-Device
specification	O
,	O
and	O
drivers	O
and	O
devices	O
that	O
do	O
obey	O
a	O
read-only	O
indication	O
may	O
give	O
the	O
user	O
a	O
way	O
to	O
override	O
it	O
.	O
</s>
<s>
The	O
miniSD	B-Device
and	O
microSD	O
formats	O
do	O
not	O
directly	O
support	O
a	O
write	O
protection	O
notch	O
,	O
but	O
they	O
can	O
be	O
inserted	O
into	O
full-size	O
adapters	O
which	O
do	O
.	O
</s>
<s>
When	O
looking	O
at	O
the	O
SD	B-Device
card	I-Device
from	O
the	O
top	O
,	O
the	O
right	O
side	O
(	O
the	O
side	O
with	O
the	O
beveled	O
corner	O
)	O
must	O
be	O
notched	O
.	O
</s>
<s>
A	O
host	O
device	O
can	O
lock	O
an	O
SD	B-Device
card	I-Device
using	O
a	O
password	O
of	O
up	O
to	O
16bytes	O
,	O
typically	O
supplied	O
by	O
the	O
user	O
.	O
</s>
<s>
Windows	B-Application
Phone	O
7	O
devices	O
use	O
SD	B-Device
cards	I-Device
designed	O
for	O
access	O
only	O
by	O
the	O
phone	O
manufacturer	O
or	O
mobile	O
provider	O
.	O
</s>
<s>
An	O
SD	B-Device
card	I-Device
inserted	O
into	O
the	O
phone	O
underneath	O
the	O
battery	O
compartment	O
becomes	O
locked	O
"	O
to	O
the	O
phone	O
with	O
an	O
automatically	O
generated	O
key	O
"	O
so	O
that	O
"	O
the	O
SD	B-Device
card	I-Device
cannot	O
be	O
read	O
by	O
another	O
phone	O
,	O
device	O
,	O
or	O
PC	O
"	O
.	O
</s>
<s>
Symbian	B-Operating_System
devices	O
,	O
however	O
,	O
are	O
some	O
of	O
the	O
few	O
that	O
can	O
perform	O
the	O
necessary	O
low-level	O
format	O
operations	O
on	O
locked	O
SD	B-Device
cards	I-Device
.	O
</s>
<s>
It	O
is	O
therefore	O
possible	O
to	O
use	O
a	O
device	O
such	O
as	O
the	O
Nokia	B-Language
N8	I-Language
to	O
reformat	O
the	O
card	O
for	O
subsequent	O
use	O
in	O
other	O
devices	O
.	O
</s>
<s>
A	O
smartSD	O
memory	B-Device
card	I-Device
is	O
a	O
microSD	O
card	O
with	O
an	O
internal	O
"	O
secure	O
element	O
"	O
that	O
allows	O
the	O
transfer	O
of	O
ISO	O
7816	O
Application	O
Protocol	O
Data	O
Unit	O
commands	O
to	O
,	O
for	O
example	O
,	O
JavaCard	B-Language
applets	O
running	O
on	O
the	O
internal	O
secure	O
element	O
through	O
the	O
SD	B-Device
bus	O
.	O
</s>
<s>
Some	O
of	O
the	O
earliest	O
versions	O
of	O
microSD	O
memory	B-Device
cards	I-Device
with	O
secure	O
elements	O
were	O
developed	O
in	O
2009	O
by	O
DeviceFidelity	O
,	O
Inc.	O
,	O
a	O
pioneer	O
in	O
near	O
field	O
communication	O
(	O
NFC	O
)	O
and	O
mobile	O
payments	O
,	O
with	O
the	O
introduction	O
of	O
In2Pay	O
and	O
CredenSE	O
products	O
,	O
later	O
commercialized	O
and	O
certified	O
for	O
mobile	O
contactless	O
transactions	O
by	O
Visa	O
in	O
2010	O
.	O
</s>
<s>
Integrated	O
Wi-Fi	O
–	O
Several	O
companies	O
produce	O
SD	B-Device
cards	I-Device
with	O
built-in	O
Wi-Fi	O
transceivers	O
supporting	O
static	O
security	O
(	O
WEP	O
40	O
;	O
104	O
;	O
and	O
128	O
,	O
WPA-PSK	O
,	O
and	O
WPA2-PSK	O
)	O
.	O
</s>
<s>
The	O
card	O
lets	O
any	O
digital	B-Device
camera	I-Device
with	O
an	O
SD	B-Device
slot	I-Device
transmit	O
captured	O
images	O
over	O
a	O
wireless	O
network	O
,	O
or	O
store	O
the	O
images	O
on	O
the	O
card	O
's	O
memory	O
until	O
it	O
is	O
in	O
range	O
of	O
a	O
wireless	O
network	O
.	O
</s>
<s>
Examples	O
include	O
:	O
Eye-Fi	O
/	O
SanDisk	O
,	O
Transcend	O
Wi-Fi	O
,	O
Toshiba	O
FlashAir	O
,	O
Trek	B-Device
Flucard	I-Device
,	O
PQI	O
Air	O
Card	O
and	O
LZeal	O
ez	O
Share	O
.	O
</s>
<s>
Pre-loaded	O
content	O
–	O
In	O
2006	O
,	O
SanDisk	O
announced	O
Gruvi	B-Device
,	O
a	O
microSD	O
card	O
with	O
extra	O
digital	O
rights	O
management	O
features	O
,	O
which	O
they	O
intended	O
as	O
a	O
medium	O
for	O
publishing	O
content	O
.	O
</s>
<s>
SanDisk	O
again	O
announced	O
pre-loaded	O
cards	O
in	O
2008	O
,	O
under	O
the	O
slotMusic	O
name	O
,	O
this	O
time	O
not	O
using	O
any	O
of	O
the	O
DRM	O
capabilities	O
of	O
the	O
SD	B-Device
card	I-Device
.	O
</s>
<s>
Integrated	O
USB	B-Protocol
connector	O
–	O
The	O
SanDisk	O
SD	B-Device
Plus	O
product	O
can	O
be	O
plugged	O
directly	O
into	O
a	O
USB	B-Protocol
port	O
without	O
needing	O
a	O
USB	B-Protocol
card	O
reader	O
.	O
</s>
<s>
Other	O
companies	O
introduced	O
comparable	O
products	O
,	O
such	O
as	O
the	O
Duo	O
SD	B-Device
product	O
of	O
OCZ	O
Technology	O
and	O
the	O
3	O
Way	O
(	O
microSDHC	O
,	O
SDHC	O
,	O
and	O
USB	B-Protocol
)	O
product	O
of	O
A-DATA	O
,	O
which	O
was	O
available	O
in	O
2008	O
only	O
.	O
</s>
<s>
Integrated	O
display	O
–	O
In	O
2006	O
,	O
A-DATA	O
announced	O
a	O
Super	O
Info	O
SD	B-Device
card	I-Device
with	O
a	O
digital	O
display	O
that	O
provided	O
a	O
two-character	O
label	O
and	O
showed	O
the	O
amount	O
of	O
unused	O
memory	O
on	O
the	O
card	O
.	O
</s>
<s>
A	O
SDIO	O
(	O
Secure	B-Device
Digital	I-Device
Input	B-General_Concept
Output	I-General_Concept
)	O
card	O
is	O
an	O
extension	O
of	O
the	O
SD	B-Device
specification	O
to	O
cover	O
I/O	B-General_Concept
functions	O
.	O
</s>
<s>
SDIO	O
cards	O
are	O
only	O
fully	O
functional	O
in	O
host	O
devices	O
designed	O
to	O
support	O
their	O
input-output	B-General_Concept
functions	O
(	O
typically	O
PDAs	O
like	O
the	O
Palm	O
Treo	O
,	O
but	O
occasionally	O
laptops	B-Device
or	O
mobile	O
phones	O
)	O
.	O
</s>
<s>
These	O
devices	O
can	O
use	O
the	O
SD	B-Device
slot	I-Device
to	O
support	O
GPS	O
receivers	O
,	O
modems	B-Application
,	O
barcode	B-Device
readers	I-Device
,	O
FM	O
radio	O
tuners	O
,	O
TV	O
tuners	O
,	O
RFID	B-Application
readers	O
,	O
digital	B-Device
cameras	I-Device
,	O
and	O
interfaces	O
to	O
Wi-Fi	O
,	O
Bluetooth	B-Protocol
,	O
Ethernet	O
,	O
and	O
IrDA	O
.	O
</s>
<s>
Many	O
other	O
SDIO	O
devices	O
have	O
been	O
proposed	O
,	O
but	O
it	O
is	O
now	O
more	O
common	O
for	O
I/O	B-General_Concept
devices	I-General_Concept
to	O
connect	O
using	O
the	O
USB	B-Protocol
interface	O
.	O
</s>
<s>
SDIO	O
cards	O
support	O
most	O
of	O
the	O
memory	O
commands	O
of	O
SD	B-Device
cards	I-Device
.	O
</s>
<s>
SDIO	O
cards	O
can	O
be	O
structured	O
as	O
eight	O
logical	O
cards	O
,	O
although	O
currently	O
,	O
the	O
typical	O
way	O
that	O
an	O
SDIO	O
card	O
uses	O
this	O
capability	O
is	O
to	O
structure	O
itself	O
as	O
one	O
I/O	B-General_Concept
card	O
and	O
one	O
memory	B-Device
card	I-Device
.	O
</s>
<s>
The	O
SDIO	O
and	O
SD	B-Device
interfaces	O
are	O
mechanically	O
and	O
electrically	O
identical	O
.	O
</s>
<s>
Host	O
devices	O
built	O
for	O
SDIO	O
cards	O
generally	O
accept	O
SD	B-Device
memory	I-Device
cards	I-Device
without	O
I/O	B-General_Concept
functions	O
.	O
</s>
<s>
However	O
,	O
the	O
reverse	O
is	O
not	O
true	O
,	O
because	O
host	O
devices	O
need	O
suitable	O
drivers	O
and	O
applications	O
to	O
support	O
the	O
card	O
's	O
I/O	B-General_Concept
functions	O
.	O
</s>
<s>
Inserting	O
an	O
SDIO	O
card	O
into	O
any	O
SD	B-Device
slot	I-Device
causes	O
no	O
physical	O
damage	O
nor	O
disruption	O
to	O
the	O
host	O
device	O
,	O
but	O
users	O
may	O
be	O
frustrated	O
that	O
the	O
SDIO	O
card	O
does	O
not	O
function	O
fully	O
when	O
inserted	O
into	O
a	O
seemingly	O
compatible	O
slot	O
.	O
</s>
<s>
(	O
USB	B-Protocol
and	O
Bluetooth	B-Protocol
devices	O
exhibit	O
comparable	O
compatibility	O
issues	O
,	O
although	O
to	O
a	O
lesser	O
extent	O
thanks	O
to	O
standardized	O
USB	B-Application
device	I-Application
classes	I-Application
and	O
Bluetooth	B-General_Concept
profiles	I-General_Concept
.	O
)	O
</s>
<s>
Both	O
types	O
of	O
SDIO	O
cards	O
support	O
SPI	B-Architecture
and	O
one-bit	O
SD	B-Device
bus	O
types	O
.	O
</s>
<s>
Low-Speed	O
SDIO	O
cards	O
are	O
allowed	O
to	O
also	O
support	O
the	O
four-bit	O
SD	B-Device
bus	O
;	O
Full-Speed	O
SDIO	O
cards	O
are	O
required	O
to	O
support	O
the	O
four-bit	O
SD	B-Device
bus	O
.	O
</s>
<s>
To	O
use	O
an	O
SDIO	O
card	O
as	O
a	O
"	O
combo	O
card	O
"	O
(	O
for	O
both	O
memory	O
and	O
I/O	B-General_Concept
)	O
,	O
the	O
host	O
device	O
must	O
first	O
select	O
four-bit	O
SD	B-Device
bus	O
operation	O
.	O
</s>
<s>
The	O
one-bit	O
SD	B-Device
protocol	O
was	O
derived	O
from	O
the	O
MMC	O
protocol	O
,	O
which	O
envisioned	O
the	O
ability	O
to	O
put	O
up	O
to	O
three	O
cards	O
on	O
a	O
bus	O
of	O
common	O
signal	O
lines	O
.	O
</s>
<s>
Though	O
the	O
cards	O
shared	O
clock	O
and	O
signal	O
lines	O
,	O
each	O
card	O
had	O
its	O
own	O
chip	B-Architecture
select	I-Architecture
line	O
to	O
sense	O
that	O
the	O
host	O
device	O
had	O
selected	O
it	O
.	O
</s>
<s>
The	O
SD	B-Device
protocol	O
envisioned	O
the	O
ability	O
to	O
gang	O
30	O
cards	O
together	O
without	O
separate	O
chip	B-Architecture
select	I-Architecture
lines	O
.	O
</s>
<s>
Newer	O
versions	O
of	O
the	O
SD	B-Device
specification	O
recommend	O
separate	O
lines	O
to	O
each	O
card	O
.	O
</s>
<s>
Host	O
devices	O
that	O
comply	O
with	O
newer	O
versions	O
of	O
the	O
specification	O
provide	O
backward	B-General_Concept
compatibility	I-General_Concept
and	O
accept	O
older	O
SD	B-Device
cards	I-Device
.	O
</s>
<s>
For	O
example	O
,	O
SDXC	O
host	O
devices	O
accept	O
all	O
previous	O
families	O
of	O
SD	B-Device
memory	I-Device
cards	I-Device
,	O
and	O
SDHC	O
host	O
devices	O
also	O
accept	O
standard	O
SD	B-Device
cards	I-Device
.	O
</s>
<s>
Use	O
of	O
an	O
SDIO	O
card	O
requires	O
the	O
host	O
device	O
be	O
designed	O
for	O
the	O
input/output	B-General_Concept
functions	O
the	O
card	O
provides	O
.	O
</s>
<s>
UHS-II	O
has	O
physically	O
more	O
pins	O
but	O
is	O
backwards	B-General_Concept
compatible	I-General_Concept
to	O
UHS-I	O
and	O
non-UHS	O
for	O
both	O
slot	O
and	O
card	O
.	O
</s>
<s>
Due	O
to	O
their	O
compact	O
size	O
,	O
Secure	B-Device
Digital	I-Device
cards	I-Device
are	O
used	O
in	O
many	O
consumer	O
electronic	O
devices	O
,	O
and	O
have	O
become	O
a	O
widespread	O
means	O
of	O
storing	O
several	O
gigabytes	O
of	O
data	O
in	O
a	O
small	O
size	O
.	O
</s>
<s>
Devices	O
in	O
which	O
the	O
user	O
may	O
remove	O
and	O
replace	O
cards	O
often	O
,	O
such	O
as	O
digital	B-Device
cameras	I-Device
,	O
camcorders	O
,	O
and	O
video	B-Device
game	I-Device
consoles	I-Device
,	O
tend	O
to	O
use	O
full-sized	O
cards	O
.	O
</s>
<s>
Devices	O
in	O
which	O
small	O
size	O
is	O
paramount	O
,	O
such	O
as	O
mobile	O
phones	O
,	O
action	B-Device
cameras	I-Device
such	O
as	O
the	O
GoPro	O
Hero	O
series	O
,	O
and	O
camera	O
drones	O
,	O
tend	O
to	O
use	O
microSD	O
cards	O
.	O
</s>
<s>
The	O
microSD	O
card	O
has	O
helped	O
propel	O
the	O
smartphone	B-Application
market	O
by	O
giving	O
both	O
manufacturers	O
and	O
consumers	O
greater	O
flexibility	O
and	O
freedom	O
.	O
</s>
<s>
While	O
cloud	O
storage	O
depends	O
on	O
stable	O
internet	O
connection	O
and	O
sufficiently	O
voluminous	O
data	O
plans	O
,	O
memory	B-Device
cards	I-Device
in	O
mobile	O
devices	O
provide	O
location-independent	O
and	O
private	O
storage	O
expansion	O
with	O
much	O
higher	O
transfer	O
rates	O
and	O
no	O
network	B-Protocol
delay	I-Protocol
,	O
enabling	O
applications	O
such	O
as	O
photography	O
and	O
video	B-Application
recording	I-Application
.	O
</s>
<s>
While	O
data	O
stored	O
internally	O
on	O
bricked	O
devices	O
is	O
inaccessible	B-General_Concept
,	O
data	O
stored	O
on	O
the	O
memory	B-Device
card	I-Device
can	O
be	O
salvaged	O
and	O
accessed	O
externally	O
by	O
the	O
user	O
as	O
mass	B-Device
storage	I-Device
device	I-Device
.	O
</s>
<s>
A	O
benefit	O
over	O
USB	B-Protocol
on	O
the	O
go	O
storage	O
expansion	O
is	O
uncompromised	O
ergonomy	O
.	O
</s>
<s>
The	O
usage	O
of	O
a	O
memory	B-Device
card	I-Device
also	O
protects	O
the	O
mobile	O
phone	O
's	O
non-replaceable	O
internal	O
storage	O
from	O
weardown	O
from	O
heavy	O
applications	O
such	O
as	O
excessive	O
camera	O
usage	O
and	O
portable	O
FTP	B-Protocol
server	I-Protocol
hosting	O
over	O
WiFi	O
Direct	O
.	O
</s>
<s>
Due	O
to	O
the	O
technical	O
development	O
of	O
memory	B-Device
cards	I-Device
,	O
users	O
of	O
existing	O
mobile	O
devices	O
are	O
able	O
to	O
expand	O
their	O
storage	O
further	O
and	O
priceworthier	O
with	O
time	O
.	O
</s>
<s>
Recent	O
versions	O
of	O
major	O
operating	O
systems	O
such	O
as	O
Windows	B-Operating_System
Mobile	I-Operating_System
and	O
Android	B-Application
allow	O
applications	O
to	O
run	O
from	O
microSD	O
cards	O
,	O
creating	O
possibilities	O
for	O
new	O
usage	O
models	O
for	O
SD	B-Device
cards	I-Device
in	O
mobile	O
computing	O
markets	O
,	O
as	O
well	O
as	O
clearing	O
available	O
internal	O
storage	O
space	O
.	O
</s>
<s>
SD	B-Device
cards	I-Device
are	O
not	O
the	O
most	O
economical	O
solution	O
in	O
devices	O
that	O
need	O
only	O
a	O
small	O
amount	O
of	O
non-volatile	B-General_Concept
memory	I-General_Concept
,	O
such	O
as	O
station	O
presets	O
in	O
small	O
radios	O
.	O
</s>
<s>
They	O
may	O
also	O
not	O
present	O
the	O
best	O
choice	O
for	O
applications	O
that	O
require	O
higher	O
storage	O
capacities	O
or	O
speeds	O
as	O
provided	O
by	O
other	O
flash	B-Device
card	O
standards	O
such	O
as	O
CompactFlash	B-Device
.	O
</s>
<s>
These	O
limitations	O
may	O
be	O
addressed	O
by	O
evolving	O
memory	O
technologies	O
,	O
such	O
as	O
the	O
new	O
SD	B-Device
7.0	O
specifications	O
which	O
allow	O
storage	O
capabilities	O
of	O
up	O
to	O
128	O
TB	O
.	O
</s>
<s>
Many	O
personal	B-Device
computers	I-Device
of	O
all	O
types	O
,	O
including	O
tablets	B-Device
and	O
mobile	O
phones	O
,	O
use	O
SD	B-Device
cards	I-Device
,	O
either	O
through	O
built-in	O
slots	O
or	O
through	O
an	O
active	O
electronic	O
adapter	O
.	O
</s>
<s>
Adapters	O
exist	O
for	O
the	O
PC	B-Architecture
card	I-Architecture
,	O
ExpressBus	O
,	O
USB	B-Protocol
,	O
FireWire	B-Protocol
,	O
and	O
the	O
parallel	B-Device
printer	I-Device
port	I-Device
.	O
</s>
<s>
Active	O
adapters	O
also	O
let	O
SD	B-Device
cards	I-Device
be	O
used	O
in	O
devices	O
designed	O
for	O
other	O
formats	O
,	O
such	O
as	O
CompactFlash	B-Device
.	O
</s>
<s>
The	O
FlashPath	B-Device
adapter	O
lets	O
SD	B-Device
cards	I-Device
be	O
used	O
in	O
a	O
floppy	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
Some	O
devices	O
such	O
as	O
the	O
Samsung	B-Application
Galaxy	I-Application
Fit	I-Application
(	O
2011	O
)	O
and	O
Samsung	B-Device
Galaxy	I-Device
Note	I-Device
8.0	I-Device
(	O
2013	O
)	O
have	O
an	O
SD	B-Device
card	I-Device
compartment	O
located	O
externally	O
and	O
accessible	O
by	O
hand	O
,	O
while	O
it	O
is	O
located	O
under	O
the	O
battery	O
cover	O
on	O
other	O
devices	O
.	O
</s>
<s>
More	O
recent	O
mobile	O
phones	O
use	O
a	O
pin-hole	O
ejection	O
system	O
for	O
the	O
tray	O
which	O
houses	O
both	O
the	O
memory	B-Device
card	I-Device
and	O
SIM	O
card	O
.	O
</s>
<s>
Commonly	O
found	O
on	O
the	O
market	O
are	O
mislabeled	O
or	O
counterfeit	O
Secure	B-Device
Digital	I-Device
cards	I-Device
that	O
report	O
a	O
fake	O
capacity	O
or	O
run	O
slower	O
than	O
labeled	O
.	O
</s>
<s>
Detection	O
of	O
counterfeit	O
cards	O
usually	O
involves	O
copying	O
files	O
with	O
random	O
data	O
to	O
the	O
SD	B-Device
card	I-Device
until	O
the	O
card	O
's	O
capacity	O
is	O
reached	O
,	O
and	O
copying	O
them	O
back	O
.	O
</s>
<s>
MD5	B-Device
)	O
,	O
or	O
trying	O
to	O
compress	B-General_Concept
them	O
.	O
</s>
<s>
SD/MMC	O
cards	O
replaced	O
Toshiba	O
's	O
SmartMedia	B-Operating_System
as	O
the	O
dominant	O
memory	B-Device
card	I-Device
format	O
used	O
in	O
digital	B-Device
cameras	I-Device
.	O
</s>
<s>
In	O
2001	O
,	O
SmartMedia	B-Operating_System
had	O
achieved	O
nearly	O
50%	O
use	O
,	O
but	O
by	O
2005	O
SD/MMC	O
had	O
achieved	O
over	O
40%	O
of	O
the	O
digital	B-Device
camera	I-Device
market	O
and	O
SmartMedia	B-Operating_System
's	O
share	O
had	O
plummeted	O
by	O
2007	O
.	O
</s>
<s>
At	O
this	O
time	O
,	O
all	O
the	O
leading	O
digital	B-Device
camera	I-Device
manufacturers	O
used	O
SD	B-Device
in	O
their	O
consumer	O
product	O
lines	O
,	O
including	O
Canon	O
,	O
Casio	O
,	O
Fujifilm	O
,	O
Kodak	O
,	O
Leica	O
,	O
Nikon	B-Algorithm
,	O
Olympus	O
,	O
Panasonic	O
,	O
Pentax	B-Application
,	O
Ricoh	O
,	O
Samsung	B-Application
,	O
and	O
Sony	O
.	O
</s>
<s>
Formerly	O
,	O
Olympus	O
and	O
Fujifilm	O
used	O
XD-Picture	O
Cards	O
(	O
xD	O
cards	O
)	O
exclusively	O
,	O
while	O
Sony	O
only	O
used	O
Memory	O
Stick	O
;	O
by	O
early	O
2010	O
all	O
three	O
supported	O
SD	B-Device
.	O
</s>
<s>
Some	O
prosumer	O
and	O
professional	O
digital	B-Device
cameras	I-Device
continued	O
to	O
offer	O
CompactFlash	B-Device
(	O
CF	B-Device
)	O
,	O
either	O
on	O
a	O
second	O
card	O
slot	O
or	O
as	O
the	O
only	O
storage	O
,	O
as	O
CF	B-Device
supports	O
much	O
higher	O
maximum	O
capacities	O
and	O
historically	O
was	O
cheaper	O
for	O
the	O
same	O
capacity	O
.	O
</s>
<s>
Secure	B-Device
Digital	I-Device
memory	B-Device
cards	I-Device
can	O
be	O
used	O
in	O
Sony	O
XDCAM	O
EX	O
camcorders	O
with	O
an	O
adapter	O
and	O
in	O
Panasonic	O
P2	B-Device
card	I-Device
equipment	O
with	O
a	O
MicroP2	O
adapter	O
.	O
</s>
<s>
Although	O
many	O
personal	B-Device
computers	I-Device
accommodate	O
SD	B-Device
cards	I-Device
as	O
an	O
auxiliary	O
storage	B-General_Concept
device	I-General_Concept
using	O
a	O
built-in	O
slot	O
,	O
or	O
can	O
accommodate	O
SD	B-Device
cards	I-Device
by	O
means	O
of	O
a	O
USB	B-Protocol
adapter	O
,	O
SD	B-Device
cards	I-Device
cannot	O
be	O
used	O
as	O
the	O
primary	O
hard	B-Device
disk	I-Device
through	O
the	O
onboard	O
ATA	O
controller	O
,	O
because	O
none	O
of	O
the	O
SD	B-Device
card	I-Device
variants	O
support	O
ATA	O
signalling	O
.	O
</s>
<s>
Primary	O
hard	B-Device
disk	I-Device
use	O
requires	O
a	O
separate	O
SD	B-Device
host	O
controller	O
or	O
an	O
SD-to-CompactFlash	O
converter	O
.	O
</s>
<s>
However	O
,	O
on	O
computers	O
that	O
support	O
bootstrapping	B-Application
from	O
a	O
USB	B-Protocol
interface	O
,	O
an	O
SD	B-Device
card	I-Device
in	O
a	O
USB	B-Protocol
adapter	O
can	O
be	O
the	O
boot	B-Operating_System
disk	O
,	O
provided	O
it	O
contains	O
an	O
operating	O
system	O
that	O
supports	O
USB	B-Protocol
access	O
once	O
the	O
bootstrap	O
is	O
complete	O
.	O
</s>
<s>
In	O
laptop	B-Device
and	O
tablet	B-Device
computers	I-Device
,	O
memory	B-Device
cards	I-Device
in	O
an	O
integrated	O
memory	B-Device
card	I-Device
reader	I-Device
offer	O
an	O
ergonomical	O
benefit	O
over	O
USB	B-Protocol
flash	B-Device
drives	I-Device
,	O
as	O
the	O
latter	O
sticks	O
out	O
of	O
the	O
device	O
,	O
and	O
the	O
user	O
would	O
need	O
to	O
be	O
cautious	O
not	O
to	O
bump	O
it	O
while	O
transporting	O
the	O
device	O
,	O
which	O
could	O
damage	O
the	O
USB	B-Protocol
port	O
.	O
</s>
<s>
Memory	B-Device
cards	I-Device
have	O
a	O
unified	O
shape	O
and	O
do	O
not	O
reserve	O
a	O
USB	B-Protocol
port	O
when	O
inserted	O
into	O
a	O
computer	O
's	O
dedicated	O
card	O
slot	O
.	O
</s>
<s>
Since	O
late	O
2009	O
,	O
newer	O
Apple	O
computers	O
with	O
installed	O
SD	B-Device
card	I-Device
readers	O
have	O
been	O
able	O
to	O
boot	B-Operating_System
in	O
macOS	B-Application
from	O
SD	B-Device
storage	O
devices	O
,	O
when	O
properly	O
formatted	O
to	O
Mac	B-Application
OS	I-Application
Extended	I-Application
file	O
format	O
and	O
the	O
default	O
partition	O
table	O
set	O
to	O
GUID	B-Application
Partition	I-Application
Table	I-Application
.	O
</s>
<s>
(	O
See	O
Other	O
file	B-Application
systems	I-Application
below	O
)	O
.	O
</s>
<s>
SD	B-Device
cards	I-Device
are	O
increasing	O
in	O
usage	O
and	O
popularity	O
among	O
owners	O
of	O
vintage	O
computers	O
like	O
8-bit	B-Device
Atari	I-Device
.	O
</s>
<s>
For	O
example	O
SIO2SD	O
(	O
SIO	B-Architecture
is	O
an	O
Atari	O
port	O
for	O
connecting	O
external	O
devices	O
)	O
is	O
used	O
nowadays	O
.	O
</s>
<s>
Software	O
for	O
an	O
8-bit	B-Device
Atari	I-Device
may	O
be	O
included	O
on	O
one	O
SD	B-Device
card	I-Device
that	O
may	O
have	O
less	O
than	O
4-8	O
GB	O
of	O
disk	O
size	O
(	O
2019	O
)	O
.	O
</s>
<s>
In	O
2008	O
,	O
the	O
SDA	O
specified	O
Embedded	O
SD	B-Device
,	O
"leverag[ing]	O
well-known	O
SD	B-Device
standards	O
"	O
to	O
enable	O
non-removable	O
SD-style	O
devices	O
on	O
printed	O
circuit	O
boards	O
.	O
</s>
<s>
However	O
this	O
standard	O
was	O
not	O
adopted	O
by	O
the	O
market	O
while	O
the	O
MMC	O
standard	O
became	O
the	O
de	O
facto	O
standard	O
for	O
embedded	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
Most	O
modern	O
microcontrollers	B-Architecture
have	O
built-in	O
SPI	B-Architecture
logic	O
that	O
can	O
interface	O
to	O
an	O
SD	B-Device
card	I-Device
operating	O
in	O
its	O
SPI	B-Architecture
mode	O
,	O
providing	O
non-volatile	B-General_Concept
storage	I-General_Concept
.	O
</s>
<s>
Even	O
if	O
a	O
microcontroller	B-Architecture
lacks	O
the	O
SPI	B-Architecture
feature	O
,	O
the	O
feature	O
can	O
be	O
emulated	O
by	O
bit	B-Algorithm
banging	I-Algorithm
.	O
</s>
<s>
For	O
example	O
,	O
a	O
home-brew	O
hack	O
combines	O
spare	O
General	B-Architecture
Purpose	I-Architecture
Input/Output	I-Architecture
(	O
GPIO	B-Architecture
)	O
pins	O
of	O
the	O
processor	O
of	O
the	O
Linksys	B-Application
WRT54G	I-Application
router	O
with	O
MMC	O
support	O
code	O
from	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
Prerecorded	O
microSDs	O
have	O
been	O
used	O
to	O
commercialize	O
music	O
under	O
the	O
brands	O
slotMusic	O
and	O
slotRadio	B-Device
by	O
SanDisk	O
and	O
MQS	O
by	O
Astell	O
&	O
Kern	O
.	O
</s>
<s>
The	O
SD	B-Device
card	I-Device
specification	O
defines	O
three	O
physical	O
sizes	O
.	O
</s>
<s>
The	O
SD	B-Device
and	O
SDHC	O
families	O
are	O
available	O
in	O
all	O
three	O
sizes	O
,	O
but	O
the	O
SDXC	O
and	O
SDUC	O
families	O
are	O
not	O
available	O
in	O
the	O
mini	O
size	O
,	O
and	O
the	O
SDIO	O
family	O
is	O
not	O
available	O
in	O
the	O
micro	O
size	O
.	O
</s>
<s>
The	O
micro	O
form	O
factor	O
is	O
the	O
smallest	O
SD	B-Device
card	I-Device
format	O
.	O
</s>
<s>
The	O
SPI	B-Architecture
bus	I-Architecture
mode	O
and	O
one-bit	O
SD	B-Device
bus	O
mode	O
are	O
mandatory	O
for	O
all	O
SD	B-Device
families	O
,	O
as	O
explained	O
in	O
the	O
next	O
section	O
.	O
</s>
<s>
Once	O
the	O
host	O
device	O
and	O
the	O
SD	B-Device
card	I-Device
negotiate	O
a	O
bus	O
interface	O
mode	O
,	O
the	O
usage	O
of	O
the	O
numbered	O
pins	O
is	O
the	O
same	O
for	O
all	O
card	O
sizes	O
.	O
</s>
<s>
SPI	B-Architecture
bus	I-Architecture
mode	O
:	O
Serial	B-Architecture
Peripheral	I-Architecture
Interface	I-Architecture
Bus	I-Architecture
is	O
primarily	O
used	O
by	O
embedded	O
microcontrollers	B-Architecture
.	O
</s>
<s>
One-bit	O
SD	B-Device
bus	O
mode	O
:	O
Separate	O
command	O
and	O
data	O
channels	O
and	O
a	O
proprietary	B-Device
transfer	O
format	O
.	O
</s>
<s>
Four-bit	O
SD	B-Device
bus	O
mode	O
:	O
Uses	O
extra	O
pins	O
plus	O
some	O
reassigned	O
pins	O
.	O
</s>
<s>
This	O
is	O
the	O
same	O
protocol	O
as	O
the	O
one-bit	O
SD	B-Device
bus	O
mode	O
which	O
uses	O
one	O
command	O
and	O
four	O
data	O
lines	O
for	O
faster	O
data	O
transfer	O
.	O
</s>
<s>
All	O
SD	B-Device
cards	I-Device
support	O
this	O
mode	O
.	O
</s>
<s>
Two	O
differential	O
lines	O
SD	B-Device
UHS-II	O
mode	O
:	O
Uses	O
two	O
low-voltage	O
differential	O
interfaces	O
to	O
transfer	O
commands	O
and	O
data	O
.	O
</s>
<s>
UHS-II	O
cards	O
include	O
this	O
interface	O
in	O
addition	O
to	O
the	O
SD	B-Device
bus	O
modes	O
.	O
</s>
<s>
The	O
physical	O
interface	O
comprises	O
9	O
pins	O
,	O
except	O
that	O
the	O
miniSD	B-Device
card	O
adds	O
two	O
unconnected	O
pins	O
in	O
the	O
center	O
and	O
the	O
microSD	O
card	O
omits	O
one	O
of	O
the	O
two	O
VSS	O
(	O
Ground	O
)	O
pins	O
.	O
</s>
<s>
+	O
SPI	B-Architecture
bus	I-Architecture
mode	O
MMCpin	O
SDpin	O
miniSDpin	O
microSDpin	O
Name	O
I/O	B-General_Concept
Logic	O
Description	O
1	O
1	O
1	O
2	O
nCS	O
I	O
PP	O
SPI	B-Architecture
Card	O
Select	O
 [ CS ] 	O
(	O
Negative	O
logic	O
)	O
2	O
2	O
2	O
3	O
DI	O
I	O
PP	O
SPI	B-Architecture
Serial	O
Data	O
In	O
 [ MOSI ] 	O
3	O
3	O
3	O
VSS	O
S	O
S	O
Ground	O
4	O
4	O
4	O
4	O
VDD	O
S	O
S	O
Power	O
5	O
5	O
5	O
5	O
CLK	O
I	O
PP	O
SPI	B-Architecture
Serial	O
Clock	O
 [ SCLK ] 	O
6	O
6	O
6	O
6	O
VSS	O
S	O
S	O
Ground	O
7	O
7	O
7	O
7	O
DO	O
O	O
PP	O
SPI	B-Architecture
Serial	O
Data	O
Out	O
 [ MISO ] 	O
8	O
8	O
8	O
NCnIRQ	O
.O	O
.OD	O
Unused	O
(	O
memory	B-Device
cards	I-Device
)	O
Interrupt	O
(	O
SDIO	O
cards	O
)	O
(	O
negative	O
logic	O
)	O
9	O
9	O
1	O
NC	O
.	O
</s>
<s>
+	O
One-bit	O
SD	B-Device
bus	O
mode	O
MMCpin	O
SDpin	O
miniSDpin	O
microSDpin	O
Name	O
I/O	B-General_Concept
Logic	O
Description	O
1	O
1	O
1	O
2	O
CD	O
I/O	B-General_Concept
.	O
</s>
<s>
Card	O
detection	O
(	O
by	O
host	O
)	O
,	O
andnon-SPI	O
mode	O
detection	O
(	O
by	O
card	O
)	O
2	O
2	O
2	O
3	O
CMD	O
I/O	B-General_Concept
PP	O
,	O
OD	O
Command	O
,	O
Response	O
3	O
3	O
3	O
VSS	O
S	O
S	O
Ground	O
4	O
4	O
4	O
4	O
VDD	O
S	O
S	O
Power	O
5	O
5	O
5	O
5	O
CLK	O
I	O
PP	O
Serial	O
clock	O
6	O
6	O
6	O
6	O
VSS	O
S	O
S	O
Ground	O
7	O
7	O
7	O
7	O
DAT0	O
I/O	B-General_Concept
PP	O
SD	B-Device
Serial	O
Data	O
0	O
8	O
8	O
8	O
NCnIRQ	O
.O	O
.OD	O
Unused	O
(	O
memory	B-Device
cards	I-Device
)	O
Interrupt	O
(	O
SDIO	O
cards	O
)	O
(	O
negative	O
Logic	O
)	O
9	O
9	O
1	O
NC	O
.	O
</s>
<s>
+	O
Four-bit	O
SD	B-Device
bus	O
mode	O
MMCpin	O
SDpin	O
miniSDpin	O
microSDpin	O
Name	O
I/O	B-General_Concept
Logic	O
Description	O
.	O
</s>
<s>
1	O
1	O
2	O
DAT3	O
I/O	B-General_Concept
PP	O
SD	B-Device
Serial	O
Data	O
3	O
.	O
</s>
<s>
2	O
2	O
3	O
CMD	O
I/O	B-General_Concept
PP	O
,	O
OD	O
Command	O
,	O
Response	O
.	O
</s>
<s>
7	O
7	O
7	O
DAT0	O
I/O	B-General_Concept
PP	O
SD	B-Device
Serial	O
Data	O
0	O
8	O
8	O
8	O
DAT1nIRQ	O
I/OO	O
PPOD	O
SD	B-Device
Serial	O
Data	O
1	O
(	O
memory	B-Device
cards	I-Device
)	O
Interrupt	O
Period	O
(	O
SDIO	O
cards	O
share	O
pin	O
via	O
protocol	O
)	O
9	O
9	O
1	O
DAT2	O
I/O	B-General_Concept
PP	O
SD	B-Device
Serial	O
Data	O
2	O
10	O
NC	O
.	O
</s>
<s>
SD	B-Device
cards	I-Device
and	O
host	O
devices	O
initially	O
communicate	O
through	O
a	O
synchronous	O
one-bit	O
interface	O
,	O
where	O
the	O
host	O
device	O
provides	O
a	O
clock	O
signal	O
that	O
strobes	O
single	O
bits	O
in	O
and	O
out	O
of	O
the	O
SD	B-Device
card	I-Device
.	O
</s>
<s>
Prepare	O
the	O
card	O
to	O
receive	O
a	O
block	O
to	O
write	O
to	O
the	O
flash	B-Device
memory	I-Device
,	O
or	O
read	O
and	O
reply	O
with	O
the	O
contents	O
of	O
a	O
specified	O
block	O
.	O
</s>
<s>
SD	B-Device
cards	I-Device
dropped	O
support	O
for	O
some	O
of	O
the	O
commands	O
in	O
the	O
MMC	O
protocol	O
,	O
but	O
added	O
commands	O
related	O
to	O
copy	O
protection	O
.	O
</s>
<s>
By	O
using	O
only	O
commands	O
supported	O
by	O
both	O
standards	O
until	O
determining	O
the	O
type	O
of	O
card	O
inserted	O
,	O
a	O
host	O
device	O
can	O
accommodate	O
both	O
SD	B-Device
and	O
MMC	O
cards	O
.	O
</s>
<s>
All	O
SD	B-Device
card	I-Device
families	O
initially	O
use	O
a	O
3.3volt	O
electrical	O
interface	O
.	O
</s>
<s>
At	O
initial	O
power-up	O
or	O
card	O
insertion	O
,	O
the	O
host	O
device	O
selects	O
either	O
the	O
Serial	B-Architecture
Peripheral	I-Architecture
Interface	I-Architecture
(	O
SPI	B-Architecture
)	O
bus	O
or	O
the	O
one-bit	O
SD	B-Device
bus	O
by	O
the	O
voltage	O
level	O
present	O
on	O
Pin	O
1	O
.	O
</s>
<s>
Thereafter	O
,	O
the	O
host	O
device	O
may	O
issue	O
a	O
command	O
to	O
switch	O
to	O
the	O
four-bit	O
SD	B-Device
bus	O
interface	O
,	O
if	O
the	O
SD	B-Device
card	I-Device
supports	O
it	O
.	O
</s>
<s>
For	O
various	O
card	O
types	O
,	O
support	O
for	O
the	O
four-bit	O
SD	B-Device
bus	O
is	O
either	O
optional	O
or	O
mandatory	O
.	O
</s>
<s>
After	O
determining	O
that	O
the	O
SD	B-Device
card	I-Device
supports	O
it	O
,	O
the	O
host	O
device	O
can	O
also	O
command	O
the	O
SD	B-Device
card	I-Device
to	O
switch	O
to	O
a	O
higher	O
transfer	O
speed	O
.	O
</s>
<s>
SD	B-Device
cards	I-Device
other	O
than	O
SDIO	O
(	O
see	O
below	O
)	O
have	O
a	O
"	O
Default	O
Speed	O
"	O
clock	O
rate	O
of	O
25MHz	O
.	O
</s>
<s>
The	O
SD	B-Device
specification	O
defines	O
four-bit-wide	O
transfers	O
.	O
</s>
<s>
Advanced	O
SD	B-Device
families	O
have	O
also	O
improved	O
speed	O
by	O
offering	O
faster	O
clock	O
frequencies	O
and	O
double	O
data	O
rate	O
(	O
explained	O
here	O
)	O
in	O
a	O
high-speed	O
differential	O
interface	O
(	O
UHS-II	O
)	O
.	O
</s>
<s>
Like	O
other	O
types	O
of	O
flash	B-Device
memory	I-Device
card	I-Device
,	O
an	O
SD	B-Device
card	I-Device
of	O
any	O
SD	B-Device
family	O
is	O
a	O
block-addressable	B-General_Concept
storage	B-General_Concept
device	I-General_Concept
,	O
in	O
which	O
the	O
host	O
device	O
can	O
read	O
or	O
write	O
fixed-size	O
blocks	O
by	O
specifying	O
their	O
block	O
number	O
.	O
</s>
<s>
Most	O
SD	B-Device
cards	I-Device
ship	O
preformatted	O
with	O
one	O
or	O
more	O
MBR	B-Device
partitions	I-Device
,	O
where	O
the	O
first	O
or	O
only	O
partition	O
contains	O
a	O
file	B-Application
system	I-Application
.	O
</s>
<s>
This	O
lets	O
them	O
operate	O
like	O
the	O
hard	B-Device
disk	I-Device
of	O
a	O
personal	B-Device
computer	I-Device
.	O
</s>
<s>
Per	O
the	O
SD	B-Device
card	I-Device
specification	O
,	O
an	O
SD	B-Device
card	I-Device
is	O
formatted	O
with	O
MBR	O
and	O
the	O
following	O
file	B-Application
system	I-Application
:	O
</s>
<s>
Most	O
consumer	O
products	O
that	O
take	O
an	O
SD	B-Device
card	I-Device
expect	O
that	O
it	O
is	O
partitioned	O
and	O
formatted	O
in	O
this	O
way	O
.	O
</s>
<s>
Universal	O
support	O
for	O
FAT12	B-Application
,	O
FAT16	B-Application
,	O
FAT16B	B-Application
,	O
and	O
FAT32	B-Application
allows	O
the	O
use	O
of	O
SDSC	O
and	O
SDHC	O
cards	O
on	O
most	O
host	O
computers	O
with	O
a	O
compatible	O
SD	B-Device
reader	O
,	O
to	O
present	O
the	O
user	O
with	O
the	O
familiar	O
method	O
of	O
named	O
files	O
in	O
a	O
hierarchical	O
directory	O
tree	O
.	O
</s>
<s>
On	O
such	O
SD	B-Device
cards	I-Device
,	O
standard	O
utility	O
programs	O
such	O
as	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
's	O
""	O
or	O
Windows	B-Application
 '	O
SCANDISK	O
can	O
be	O
used	O
to	O
repair	O
a	O
corrupted	O
filing	O
system	O
and	O
sometimes	O
recover	O
deleted	O
files	O
.	O
</s>
<s>
Defragmentation	B-Application
tools	O
for	O
FAT	O
file	B-Application
systems	I-Application
may	O
be	O
used	O
on	O
such	O
cards	O
.	O
</s>
<s>
The	O
resulting	O
consolidation	O
of	O
files	O
may	O
provide	O
a	O
marginal	O
improvement	O
in	O
the	O
time	O
required	O
to	O
read	O
or	O
write	O
the	O
file	O
,	O
but	O
not	O
an	O
improvement	O
comparable	O
to	O
defragmentation	B-Application
of	O
hard	B-Device
drives	I-Device
,	O
where	O
storing	O
a	O
file	O
in	O
multiple	O
fragments	O
requires	O
additional	O
physical	O
,	O
and	O
relatively	O
slow	O
,	O
movement	O
of	O
a	O
drive	O
head	O
.	O
</s>
<s>
Moreover	O
,	O
defragmentation	B-Application
performs	O
writes	O
to	O
the	O
SD	B-Device
card	I-Device
that	O
count	O
against	O
the	O
card	O
's	O
rated	O
lifespan	O
.	O
</s>
<s>
The	O
write	O
endurance	O
of	O
the	O
physical	O
memory	O
is	O
discussed	O
in	O
the	O
article	O
on	O
flash	B-Device
memory	I-Device
;	O
newer	O
technology	O
to	O
increase	O
the	O
storage	O
capacity	O
of	O
a	O
card	O
provides	O
worse	O
write	O
endurance	O
.	O
</s>
<s>
When	O
reformatting	O
an	O
SD	B-Device
card	I-Device
with	O
a	O
capacity	O
of	O
at	O
least	O
32MB	O
(	O
65,536	O
logical	O
sectors	O
or	O
more	O
)	O
,	O
but	O
not	O
more	O
than	O
2GB	O
,	O
FAT16B	B-Application
with	O
partition	O
type	O
06h	O
and	O
EBPB	O
4.1	O
is	O
recommended	O
if	O
the	O
card	O
is	O
for	O
a	O
consumer	O
device	O
.	O
</s>
<s>
(	O
FAT16B	B-Application
is	O
also	O
an	O
option	O
for	O
4GB	O
cards	O
,	O
but	O
it	O
requires	O
the	O
use	O
of	O
64KB	O
clusters	O
,	O
which	O
are	O
not	O
widely	O
supported	O
.	O
)	O
</s>
<s>
FAT16B	B-Application
does	O
not	O
support	O
cards	O
above	O
4GB	O
at	O
all	O
.	O
</s>
<s>
The	O
SDXC	O
specification	O
mandates	O
the	O
use	O
of	O
Microsoft	O
's	O
proprietary	B-Device
exFAT	B-Application
file	I-Application
system	I-Application
,	O
which	O
sometimes	O
requires	O
appropriate	O
drivers	O
(	O
e.g.	O
</s>
<s>
exfat-utils/exfat	O
-fuse	O
on	O
Linux	B-Application
)	O
.	O
</s>
<s>
Because	O
the	O
host	O
views	O
the	O
SD	B-Device
card	I-Device
as	O
a	O
block	B-General_Concept
storage	I-General_Concept
device	O
,	O
the	O
card	O
does	O
not	O
require	O
MBR	B-Device
partitions	I-Device
or	O
any	O
specific	O
file	B-Application
system	I-Application
.	O
</s>
<s>
The	O
card	O
can	O
be	O
reformatted	O
to	O
use	O
any	O
file	B-Application
system	I-Application
the	O
operating	O
system	O
supports	O
.	O
</s>
<s>
Under	O
Windows	B-Application
,	O
SD	B-Device
cards	I-Device
can	O
be	O
formatted	O
using	O
NTFS	B-Application
and	O
,	O
on	O
later	O
versions	O
,	O
exFAT	B-Application
.	O
</s>
<s>
Under	O
macOS	B-Application
,	O
SD	B-Device
cards	I-Device
can	O
be	O
partitioned	O
as	O
GUID	B-Application
devices	O
and	O
formatted	O
with	O
either	O
HFS	B-Application
Plus	I-Application
or	O
APFS	B-Application
file	B-Application
systems	I-Application
or	O
still	O
use	O
exFAT	B-Application
.	O
</s>
<s>
Under	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
such	O
as	O
Linux	B-Application
or	O
FreeBSD	B-Operating_System
,	O
SD	B-Device
cards	I-Device
can	O
be	O
formatted	O
using	O
the	O
UFS	B-Operating_System
,	O
Ext2	B-Application
,	O
Ext3	B-Application
,	O
Ext4	B-Application
,	O
btrfs	B-Operating_System
,	O
HFS	B-Application
Plus	I-Application
,	O
ReiserFS	B-Application
or	O
F2FS	B-Application
file	B-Application
system	I-Application
.	O
</s>
<s>
Additionally	O
under	O
Linux	B-Application
,	O
HFS	B-Application
Plus	I-Application
file	B-Application
systems	I-Application
may	O
be	O
accessed	O
for	O
read/write	O
if	O
the	O
"	O
hfsplus	B-Application
"	O
package	O
is	O
installed	O
,	O
and	O
partitioned	O
and	O
formatted	O
if	O
"	O
hfsprogs	O
"	O
is	O
installed	O
.	O
</s>
<s>
(	O
These	O
package	O
names	O
are	O
correct	O
under	O
Debian	O
,	O
Ubuntu	O
etc.	O
,	O
but	O
may	O
differ	O
on	O
other	O
Linux	B-Application
distributions	O
.	O
)	O
</s>
<s>
Any	O
recent	O
version	O
of	O
the	O
above	O
can	O
format	O
SD	B-Device
cards	I-Device
using	O
the	O
UDF	O
file	B-Application
system	I-Application
.	O
</s>
<s>
Additionally	O
,	O
as	O
with	O
live	O
USB	B-Protocol
flash	B-Device
drives	I-Device
,	O
an	O
SD	B-Device
card	I-Device
can	O
have	O
an	O
operating	O
system	O
installed	O
on	O
it	O
.	O
</s>
<s>
Computers	O
that	O
can	O
boot	B-Operating_System
from	O
an	O
SD	B-Device
card	I-Device
(	O
either	O
using	O
a	O
USB	B-Protocol
adapter	O
or	O
inserted	O
into	O
the	O
computer	O
's	O
flash	B-Device
media	I-Device
reader	O
)	O
instead	O
of	O
the	O
hard	B-Device
disk	I-Device
drive	I-Device
may	O
thereby	O
be	O
able	O
to	O
recover	O
from	O
a	O
corrupted	O
hard	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
Such	O
an	O
SD	B-Device
card	I-Device
can	O
be	O
write-locked	O
to	O
preserve	O
the	O
system	O
's	O
integrity	O
.	O
</s>
<s>
The	O
SD	B-Device
Standard	O
allows	O
usage	O
of	O
only	O
the	O
above-mentioned	O
Microsoft	O
FAT	O
file	B-Application
systems	I-Application
and	O
any	O
card	O
produced	O
in	O
the	O
market	O
shall	O
be	O
preloaded	O
with	O
the	O
related	O
standard	O
file	B-Application
system	I-Application
upon	O
its	O
delivery	O
to	O
the	O
market	O
.	O
</s>
<s>
If	O
any	O
application	O
or	O
user	O
re-formats	O
the	O
card	O
with	O
a	O
non-standard	O
file	B-Application
system	I-Application
the	O
proper	O
operation	O
of	O
the	O
card	O
,	O
including	O
interoperability	O
,	O
cannot	O
be	O
assured	O
.	O
</s>
<s>
Reformatting	O
an	O
SD	B-Device
card	I-Device
with	O
a	O
different	O
file	B-Application
system	I-Application
,	O
or	O
even	O
with	O
the	O
same	O
one	O
,	O
may	O
make	O
the	O
card	O
slower	O
,	O
or	O
shorten	O
its	O
lifespan	O
.	O
</s>
<s>
Some	O
cards	O
use	O
wear	B-Application
leveling	I-Application
,	O
in	O
which	O
frequently	O
modified	O
blocks	O
are	O
mapped	O
to	O
different	O
portions	O
of	O
memory	O
at	O
different	O
times	O
,	O
and	O
some	O
wear-leveling	B-Application
algorithms	O
are	O
designed	O
for	O
the	O
access	O
patterns	O
typical	O
of	O
FAT12	B-Application
,	O
FAT16	B-Application
or	O
FAT32	B-Application
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
preformatted	O
file	B-Application
system	I-Application
may	O
use	O
a	O
cluster	O
size	O
that	O
matches	O
the	O
erase	O
region	O
of	O
the	O
physical	O
memory	O
on	O
the	O
card	O
;	O
reformatting	O
may	O
change	O
the	O
cluster	O
size	O
and	O
make	O
writes	O
less	O
efficient	O
.	O
</s>
<s>
The	O
SD	B-Device
Association	O
provides	O
freely-downloadable	O
SD	B-Device
Formatter	O
software	O
to	O
overcome	O
these	O
problems	O
for	O
Windows	B-Application
and	O
Mac	B-Operating_System
OS	I-Operating_System
X	I-Operating_System
.	O
</s>
<s>
SD/SDHC/SDXC	O
memory	B-Device
cards	I-Device
have	O
a	O
"	O
Protected	O
Area	O
"	O
on	O
the	O
card	O
for	O
the	O
SD	B-Device
standard	O
's	O
security	O
function	O
.	O
</s>
<s>
Neither	O
standard	O
formatters	O
nor	O
the	O
SD	B-Device
Association	O
formatter	O
will	O
erase	O
it	O
.	O
</s>
<s>
The	O
SD	B-Device
Association	O
suggests	O
that	O
devices	O
or	O
software	O
which	O
use	O
the	O
SD	B-Device
security	O
function	O
may	O
format	O
it	O
.	O
</s>
<s>
The	O
power	O
consumption	O
of	O
SD	B-Device
cards	I-Device
varies	O
by	O
its	O
speed	O
mode	O
,	O
manufacturer	O
and	O
model	O
.	O
</s>
<s>
If	O
there	O
is	O
data	O
transfer	O
for	O
significant	O
periods	O
,	O
battery	O
life	O
may	O
be	O
reduced	O
noticeably	O
;	O
for	O
reference	O
,	O
the	O
capacity	O
of	O
smartphone	B-Application
batteries	O
is	O
typically	O
around	O
6Wh	O
(	O
Samsung	B-Application
Galaxy	O
S2	O
:	O
1650mAh	O
@	O
3.7V	O
)	O
.	O
</s>
<s>
All	O
SD	B-Device
cards	I-Device
let	O
the	O
host	O
device	O
determine	O
how	O
much	O
information	O
the	O
card	O
can	O
hold	O
,	O
and	O
the	O
specification	O
of	O
each	O
SD	B-Device
family	O
gives	O
the	O
host	O
device	O
a	O
guarantee	O
of	O
the	O
maximum	O
capacity	O
a	O
compliant	O
card	O
reports	O
.	O
</s>
<s>
By	O
the	O
time	O
the	O
version	O
2.0	O
(	O
SDHC	O
)	O
specification	O
was	O
completed	O
in	O
June	O
2006	O
,	O
vendors	O
had	O
already	O
devised	O
2GB	O
and	O
4GB	O
SD	B-Device
cards	I-Device
,	O
either	O
as	O
specified	O
in	O
Version	O
1.01	O
,	O
or	O
by	O
creatively	O
reading	O
Version	O
1.00	O
.	O
</s>
<s>
A	O
host	O
device	O
can	O
ask	O
any	O
inserted	O
SD	B-Device
card	I-Device
for	O
its	O
128-bit	O
identification	O
string	O
(	O
the	O
Card-Specific	O
Data	O
or	O
CSD	O
)	O
.	O
</s>
<s>
SD	B-Device
version	O
1.00	O
assumed	O
512	O
bytes	O
per	O
block	O
.	O
</s>
<s>
Doing	O
so	O
enabled	O
cards	O
with	O
2GB	O
and	O
4GB	O
capacity	O
,	O
such	O
as	O
the	O
Transcend	O
4GB	O
SD	B-Device
card	I-Device
and	O
the	O
Memorette	O
4	O
GB	O
SD	B-Device
card	I-Device
.	O
</s>
<s>
In	O
version	O
1	O
of	O
the	O
SD	B-Device
specification	O
,	O
capacities	O
up	O
to	O
2GB	O
are	O
calculated	O
by	O
combining	O
fields	O
of	O
the	O
CSD	O
as	O
follows	O
:	O
</s>
<s>
Like	O
most	O
memory	B-Device
card	I-Device
formats	O
,	O
SD	B-Device
is	O
covered	O
by	O
numerous	O
patents	O
and	O
trademarks	O
.	O
</s>
<s>
Early	O
versions	O
of	O
the	O
SD	B-Device
specification	O
were	O
available	O
under	O
a	O
non-disclosure	O
agreement	O
(	O
NDA	O
)	O
prohibiting	O
development	O
of	O
open-source	B-Application
drivers	O
.	O
</s>
<s>
However	O
,	O
the	O
system	O
was	O
eventually	O
reverse-engineered	O
and	O
free	O
software	O
drivers	O
provided	O
access	O
to	O
SD	B-Device
cards	I-Device
not	O
using	O
DRM	O
.	O
</s>
<s>
Subsequent	O
to	O
the	O
release	O
of	O
most	O
open-source	B-Application
drivers	O
,	O
the	O
SDA	O
provided	O
a	O
simplified	O
version	O
of	O
the	O
specification	O
under	O
a	O
less	O
restrictive	O
license	O
helping	O
reduce	O
some	O
incompatibility	O
issues	O
.	O
</s>
<s>
Under	O
a	O
disclaimers	O
agreement	O
,	O
the	O
simplified	O
specification	O
released	O
by	O
the	O
SDA	O
in	O
2006	O
–	O
as	O
opposed	O
to	O
that	O
of	O
SD	B-Device
cards	I-Device
–	O
was	O
later	O
extended	O
to	O
the	O
physical	O
layer	O
,	O
ASSD	O
extensions	O
,	O
SDIO	O
,	O
and	O
SDIO	O
Bluetooth	B-Protocol
Type-A	O
.	O
</s>
<s>
Again	O
,	O
most	O
of	O
the	O
information	O
had	O
already	O
been	O
discovered	O
and	O
Linux	B-Application
had	O
a	O
fully	O
free	O
driver	O
for	O
it	O
.	O
</s>
<s>
Still	O
,	O
building	O
a	O
chip	O
conforming	O
to	O
this	O
specification	O
caused	O
the	O
One	O
Laptop	B-Device
per	O
Child	O
project	O
to	O
claim	O
"	O
the	O
first	O
truly	O
Open	O
Source	O
SD	B-Device
implementation	O
,	O
with	O
no	O
need	O
to	O
obtain	O
an	O
SDI	O
license	O
or	O
sign	O
NDAs	O
to	O
create	O
SD	B-Device
drivers	O
or	O
applications.	O
"	O
</s>
<s>
The	O
proprietary	B-Device
nature	O
of	O
the	O
complete	O
SD	B-Device
specification	O
affects	O
embedded	B-Architecture
systems	I-Architecture
,	O
laptop	B-Device
computers	I-Device
,	O
and	O
some	O
desktop	O
computers	O
;	O
many	O
desktop	O
computers	O
do	O
not	O
have	O
card	O
slots	O
,	O
instead	O
using	O
USB-based	O
card	O
readers	O
if	O
necessary	O
.	O
</s>
<s>
These	O
card	O
readers	O
present	O
a	O
standard	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
interface	I-Architecture
to	O
memory	B-Device
cards	I-Device
,	O
thus	O
separating	O
the	O
operating	O
system	O
from	O
the	O
details	O
of	O
the	O
underlying	O
SD	B-Device
interface	O
.	O
</s>
<s>
However	O
,	O
embedded	B-Architecture
systems	I-Architecture
(	O
such	O
as	O
portable	O
music	O
players	O
)	O
usually	O
gain	O
direct	O
access	O
to	O
SD	B-Device
cards	I-Device
and	O
thus	O
need	O
complete	O
programming	O
information	O
.	O
</s>
<s>
Desktop	O
card	O
readers	O
are	O
themselves	O
embedded	B-Architecture
systems	I-Architecture
;	O
their	O
manufacturers	O
have	O
usually	O
paid	O
the	O
SDA	O
for	O
complete	O
access	O
to	O
the	O
SD	B-Device
specifications	O
.	O
</s>
<s>
Many	O
notebook	B-Device
computers	I-Device
now	O
include	O
SD	B-Device
card	I-Device
readers	O
not	O
based	O
on	O
USB	B-Protocol
;	O
device	O
drivers	O
for	O
these	O
essentially	O
gain	O
direct	O
access	O
to	O
the	O
SD	B-Device
card	I-Device
,	O
as	O
do	O
embedded	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
The	O
SPI-bus	O
interface	O
mode	O
is	O
the	O
only	O
type	O
that	O
does	O
not	O
require	O
a	O
host	O
license	O
for	O
accessing	O
SD	B-Device
cards	I-Device
.	O
</s>
<s>
Overall	O
,	O
SD	B-Device
is	O
less	O
open	O
than	O
CompactFlash	B-Device
or	O
USB	B-Protocol
flash	B-Device
memory	I-Device
drives	O
.	O
</s>
<s>
(	O
CompactFlash	B-Device
and	O
USB	B-Protocol
flash	B-Device
drives	I-Device
may	O
require	O
licensing	O
fees	O
for	O
the	O
use	O
of	O
the	O
SDA	O
's	O
trademarked	O
logos	B-Device
.	O
)	O
</s>
<s>
However	O
,	O
SD	B-Device
is	O
much	O
more	O
open	O
than	O
Sony	O
's	O
Memory	O
Stick	O
,	O
for	O
which	O
no	O
public	O
documentation	O
nor	O
any	O
documented	O
legacy	O
implementation	O
is	O
available	O
.	O
</s>
<s>
All	O
SD	B-Device
cards	I-Device
can	O
be	O
accessed	O
freely	O
using	O
the	O
well-documented	O
SPI	B-Architecture
bus	I-Architecture
.	O
</s>
<s>
xD	O
cards	O
are	O
simply	O
18-pin	O
NAND	O
flash	B-Device
chips	I-Device
in	O
a	O
special	O
package	O
and	O
support	O
the	O
standard	O
command	O
set	O
for	O
raw	O
NAND	O
flash	B-Device
access	O
.	O
</s>
<s>
Although	O
the	O
raw	O
hardware	O
interface	O
to	O
xD	O
cards	O
is	O
well	O
understood	O
,	O
the	O
layout	O
of	O
its	O
memory	O
contents	O
—	O
necessary	O
for	O
interoperability	O
with	O
xD	O
card	O
readers	O
and	O
digital	B-Device
cameras	I-Device
—	O
is	O
totally	O
undocumented	O
.	O
</s>
<s>
A	O
malfunctioning	O
SD	B-Device
card	I-Device
can	O
be	O
repaired	O
using	O
specialized	O
equipment	O
,	O
as	O
long	O
as	O
the	O
middle	O
part	O
,	O
containing	O
the	O
flash	B-Device
storage	I-Device
,	O
is	O
not	O
physically	O
damaged	O
.	O
</s>
