<s>
EEPROM	B-General_Concept
(	O
also	O
called	O
E2PROM	B-General_Concept
)	O
stands	O
for	O
electrically	B-General_Concept
erasable	I-General_Concept
programmable	I-General_Concept
read-only	I-General_Concept
memory	I-General_Concept
and	O
is	O
a	O
type	O
of	O
non-volatile	B-General_Concept
memory	I-General_Concept
used	O
in	O
computers	O
,	O
usually	O
integrated	O
in	O
microcontrollers	B-Architecture
such	O
as	O
smart	O
cards	O
and	O
remote	O
keyless	O
systems	O
,	O
or	O
as	O
a	O
separate	O
chip	O
device	O
to	O
store	O
relatively	O
small	O
amounts	O
of	O
data	O
by	O
allowing	O
individual	O
bytes	O
to	O
be	O
erased	O
and	O
reprogrammed	O
.	O
</s>
<s>
EEPROMs	B-General_Concept
are	O
organized	O
as	O
arrays	O
of	O
floating-gate	B-Algorithm
transistors	I-Algorithm
.	O
</s>
<s>
EEPROMs	B-General_Concept
can	O
be	O
programmed	O
and	O
erased	O
in-circuit	O
,	O
by	O
applying	O
special	O
programming	O
signals	O
.	O
</s>
<s>
Originally	O
,	O
EEPROMs	B-General_Concept
were	O
limited	O
to	O
single-byte	O
operations	O
,	O
which	O
made	O
them	O
slower	O
,	O
but	O
modern	O
EEPROMs	B-General_Concept
allow	O
multi-byte	O
page	O
operations	O
.	O
</s>
<s>
An	O
EEPROM	B-General_Concept
has	O
a	O
limited	O
life	O
for	O
erasing	O
and	O
reprogramming	O
,	O
now	O
reaching	O
a	O
million	O
operations	O
in	O
modern	O
EEPROMs	B-General_Concept
.	O
</s>
<s>
In	O
an	O
EEPROM	B-General_Concept
that	O
is	O
frequently	O
reprogrammed	O
,	O
the	O
life	O
of	O
the	O
EEPROM	B-General_Concept
is	O
an	O
important	O
design	O
consideration	O
.	O
</s>
<s>
Flash	B-Device
memory	I-Device
is	O
a	O
type	O
of	O
EEPROM	B-General_Concept
designed	O
for	O
high	O
speed	O
and	O
high	O
density	O
,	O
at	O
the	O
expense	O
of	O
large	O
erase	O
blocks	O
(	O
typically	O
512bytes	O
or	O
larger	O
)	O
and	O
limited	O
number	O
of	O
write	O
cycles	O
(	O
often	O
10,000	O
)	O
.	O
</s>
<s>
There	O
is	O
no	O
clear	O
boundary	O
dividing	O
the	O
two	O
,	O
but	O
the	O
term	O
"	O
EEPROM	B-General_Concept
"	O
is	O
generally	O
used	O
to	O
describe	O
non-volatile	B-General_Concept
memory	I-General_Concept
with	O
small	O
erase	O
blocks	O
(	O
as	O
small	O
as	O
one	O
byte	O
)	O
and	O
a	O
long	O
lifetime	O
(	O
typically	O
1,000,000	O
cycles	O
)	O
.	O
</s>
<s>
Many	O
past	O
microcontrollers	B-Architecture
included	O
both	O
(	O
flash	B-Device
memory	I-Device
for	O
the	O
firmware	B-Application
and	O
a	O
small	O
EEPROM	B-General_Concept
for	O
parameters	O
)	O
,	O
though	O
the	O
trend	O
with	O
modern	O
microcontrollers	B-Architecture
is	O
to	O
emulate	B-Application
EEPROM	B-General_Concept
using	O
flash	B-Device
.	O
</s>
<s>
As	O
of	O
2020	O
,	O
flash	B-Device
memory	I-Device
costs	O
much	O
less	O
than	O
byte-programmable	O
EEPROM	B-General_Concept
and	O
is	O
the	O
dominant	O
memory	O
type	O
wherever	O
a	O
system	O
requires	O
a	O
significant	O
amount	O
of	O
non-volatile	B-General_Concept
solid-state	B-Device
storage	I-Device
.	O
</s>
<s>
EEPROMs	B-General_Concept
,	O
however	O
,	O
are	O
still	O
used	O
on	O
applications	O
that	O
only	O
require	O
small	O
amounts	O
of	O
storage	O
,	O
like	O
in	O
serial	B-General_Concept
presence	I-General_Concept
detect	I-General_Concept
.	O
</s>
<s>
In	O
the	O
early	O
1970s	O
,	O
some	O
studies	O
,	O
inventions	O
,	O
and	O
development	O
for	O
electrically	O
re-programmable	O
non-volatile	B-General_Concept
memories	I-General_Concept
were	O
performed	O
by	O
various	O
companies	O
and	O
organizations	O
.	O
</s>
<s>
They	O
fabricated	B-Architecture
an	O
EEPROM	B-General_Concept
device	O
in	O
1972	O
,	O
and	O
continued	O
this	O
study	O
for	O
more	O
than	O
10	O
years	O
.	O
</s>
<s>
which	O
used	O
Renesas	O
Electronics	O
 '	O
flash	B-Device
memory	I-Device
integrated	O
in	O
single-chip	O
microcontrollers	B-Architecture
.	O
</s>
<s>
In	O
1972	O
,	O
a	O
type	O
of	O
electrically	O
re-programmable	O
non-volatile	B-General_Concept
memory	I-General_Concept
was	O
invented	O
by	O
Fujio	O
Masuoka	O
at	O
Toshiba	O
,	O
who	O
is	O
also	O
known	O
as	O
the	O
inventor	O
of	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
studied	O
,	O
invented	O
,	O
and	O
manufactured	O
some	O
electrically	O
re-programmable	O
non-volatile	B-General_Concept
devices	O
until	O
1977	O
.	O
</s>
<s>
But	O
in	O
general	O
,	O
programmable	O
memories	O
,	O
including	O
EPROM	B-General_Concept
,	O
of	O
early	O
1970s	O
had	O
reliability	O
and	O
endurance	O
problems	O
such	O
as	O
the	O
data	O
retention	O
periods	O
and	O
the	O
number	O
of	O
erase/write	O
cycles	O
.	O
</s>
<s>
In	O
1975	O
,	O
NEC	O
's	O
semiconductor	O
operations	O
unit	O
,	O
later	O
NEC	O
Electronics	O
,	O
currently	O
Renesas	O
Electronics	O
,	O
applied	O
the	O
trademark	O
name	O
EEPROM®	O
to	O
Japan	O
Patent	O
Office	O
.	O
</s>
<s>
In	O
February	O
1977	O
,	O
Eliyahou	O
Harari	O
at	O
Hughes	O
Aircraft	O
Company	O
invented	O
a	O
new	O
EEPROM	B-General_Concept
technology	O
using	O
Fowler-Nordheim	O
tunnelling	O
through	O
a	O
thin	O
silicon	O
dioxide	O
layer	O
between	O
the	O
floating-gate	B-Algorithm
and	O
the	O
wafer	B-Architecture
.	O
</s>
<s>
Hughes	O
went	O
on	O
to	O
produce	O
this	O
new	O
EEPROM	B-General_Concept
devices	O
.	O
</s>
<s>
cited	O
IBM	O
's	O
contribution	O
of	O
EEPROM	B-General_Concept
technology	O
and	O
NEC	O
's	O
EEPROM®	O
invention	O
.	O
</s>
<s>
They	O
used	O
SONOS	O
(	O
polysilicon-oxynitride-nitride-oxide-silicon	O
)	O
structure	O
with	O
thickness	O
of	O
silicon	O
dioxide	O
less	O
than	O
30	O
Å	O
,	O
and	O
SIMOS	O
(	O
stacked-gate	O
injection	O
MOS	B-Architecture
)	O
structure	O
,	O
respectively	O
,	O
for	O
using	O
Fowler-Nordheim	O
tunnelling	O
hot-carrier	O
injection	O
.	O
</s>
<s>
Around	O
1976	O
to	O
1978	O
,	O
Intel	O
's	O
team	O
,	O
including	O
George	O
Perlegos	O
,	O
made	O
some	O
inventions	O
to	O
improve	O
this	O
tunneling	O
E2PROM	B-General_Concept
technology	O
.	O
</s>
<s>
In	O
1980	O
.	O
this	O
structure	O
was	O
publicly	O
introduced	O
as	O
FLOTOX	O
;	O
floating	B-Algorithm
gate	I-Algorithm
tunnel	O
oxide	O
.	O
</s>
<s>
which	O
used	O
on-device	O
charge	O
pumps	O
to	O
supply	O
the	O
high	O
voltages	O
necessary	O
for	O
programming	O
E2PROMs	B-General_Concept
.	O
</s>
<s>
As	O
is	O
described	O
in	O
former	O
section	O
,	O
old	O
EEPROMs	B-General_Concept
are	O
based	O
on	O
avalanche	O
breakdown-based	O
hot-carrier	O
injection	O
with	O
high	O
reverse	O
breakdown	O
voltage	O
.	O
</s>
<s>
But	O
FLOTOX	O
theoretical	O
basis	O
is	O
Fowler	O
–	O
Nordheim	O
tunneling	O
hot-carrier	O
injection	O
through	O
a	O
thin	O
silicon	O
dioxide	O
layer	O
between	O
the	O
floating	B-Algorithm
gate	I-Algorithm
and	O
the	O
wafer	B-Architecture
.	O
</s>
<s>
Theoretical	O
basis	O
of	O
the	O
physical	O
phenomenon	O
itself	O
is	O
the	O
same	O
as	O
today	O
's	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
But	O
each	O
FLOTOX	O
structure	O
is	O
in	O
conjunction	O
with	O
another	O
read-control	O
transistor	B-Application
because	O
the	O
floating	B-Algorithm
gate	I-Algorithm
itself	O
is	O
just	O
programming	O
and	O
erasing	O
one	O
data	O
bit	O
.	O
</s>
<s>
Intel	O
's	O
FLOTOX	O
device	O
structure	O
improved	O
EEPROM	B-General_Concept
reliability	O
,	O
in	O
other	O
words	O
,	O
the	O
endurance	O
of	O
the	O
write	O
and	O
erase	O
cycles	O
,	O
and	O
the	O
data	O
retention	O
period	O
.	O
</s>
<s>
Nowadays	O
,	O
EEPROM	B-General_Concept
is	O
used	O
for	O
embedded	O
microcontrollers	B-Architecture
as	O
well	O
as	O
standard	O
EEPROM	B-General_Concept
products	O
.	O
</s>
<s>
EEPROM	B-General_Concept
still	O
requires	O
a	O
2-transistor	O
structure	O
per	O
bit	O
to	O
erase	O
a	O
dedicated	O
byte	O
in	O
the	O
memory	O
,	O
while	O
flash	B-Device
memory	I-Device
has	O
1	O
transistor	B-Application
per	O
bit	O
to	O
erase	O
a	O
region	O
of	O
the	O
memory	O
.	O
</s>
<s>
Because	O
EEPROM	B-General_Concept
technology	O
is	O
used	O
for	O
some	O
security	O
gadgets	O
,	O
such	O
as	O
credit	O
card	O
,	O
SIM	O
card	O
,	O
key-less	O
entry	O
,	O
etc.	O
,	O
some	O
devices	O
have	O
security	O
protection	O
mechanisms	O
,	O
such	O
as	O
copy-protection	O
.	O
</s>
<s>
EEPROM	B-General_Concept
devices	O
use	O
a	O
serial	O
or	O
parallel	O
interface	O
for	O
data	O
input/output	O
.	O
</s>
<s>
The	O
common	O
serial	O
interfaces	O
are	O
SPI	B-Architecture
,	O
I²C	O
,	O
Microwire	O
,	O
UNI/O	O
,	O
and	O
1-Wire	O
.	O
</s>
<s>
A	O
typical	O
EEPROM	B-General_Concept
serial	O
protocol	O
consists	O
of	O
three	O
phases	O
:	O
OP-code	B-Language
phase	I-Language
,	O
address	O
phase	O
and	O
data	O
phase	O
.	O
</s>
<s>
The	O
OP-code	B-Language
is	O
usually	O
the	O
first	O
8	O
bits	O
input	O
to	O
the	O
serial	O
input	O
pin	O
of	O
the	O
EEPROM	B-General_Concept
device	O
(	O
or	O
with	O
most	O
I²C	O
devices	O
,	O
is	O
implicit	O
)	O
;	O
followed	O
by	O
8	O
to	O
24	O
bits	O
of	O
addressing	O
,	O
depending	O
on	O
the	O
depth	O
of	O
the	O
device	O
,	O
then	O
the	O
read	O
or	O
write	O
data	O
.	O
</s>
<s>
Each	O
EEPROM	B-General_Concept
device	O
typically	O
has	O
its	O
own	O
set	O
of	O
OP-code	B-Language
instructions	O
mapped	O
to	O
different	O
functions	O
.	O
</s>
<s>
Common	O
operations	O
on	O
SPI	B-Architecture
EEPROM	B-General_Concept
devices	O
are	O
:	O
</s>
<s>
Other	O
operations	O
supported	O
by	O
some	O
EEPROM	B-General_Concept
devices	O
are	O
:	O
</s>
<s>
Parallel	O
EEPROM	B-General_Concept
devices	O
typically	O
have	O
an	O
8-bit	O
data	O
bus	O
and	O
an	O
address	O
bus	O
wide	O
enough	O
to	O
cover	O
the	O
complete	O
memory	O
.	O
</s>
<s>
Some	O
microcontrollers	B-Architecture
also	O
have	O
integrated	O
parallel	O
EEPROM	B-General_Concept
.	O
</s>
<s>
Operation	O
of	O
a	O
parallel	O
EEPROM	B-General_Concept
is	O
simple	O
and	O
fast	O
when	O
compared	O
to	O
serial	O
EEPROM	B-General_Concept
,	O
but	O
these	O
devices	O
are	O
larger	O
due	O
to	O
the	O
higher	O
pin	O
count	O
(	O
28	O
pins	O
or	O
more	O
)	O
and	O
have	O
been	O
decreasing	O
in	O
popularity	O
in	O
favor	O
of	O
serial	O
EEPROM	B-General_Concept
or	O
flash	B-Device
.	O
</s>
<s>
EEPROM	B-General_Concept
memory	O
is	O
used	O
to	O
enable	O
features	O
in	O
other	O
types	O
of	O
products	O
that	O
are	O
not	O
strictly	O
memory	O
products	O
.	O
</s>
<s>
Products	O
such	O
as	O
real-time	O
clocks	O
,	O
digital	O
potentiometers	B-Device
,	O
digital	O
temperature	O
sensors	O
,	O
among	O
others	O
,	O
may	O
have	O
small	O
amounts	O
of	O
EEPROM	B-General_Concept
to	O
store	O
calibration	O
information	O
or	O
other	O
data	O
that	O
needs	O
to	O
be	O
available	O
in	O
the	O
event	O
of	O
power	O
loss	O
.	O
</s>
<s>
It	O
was	O
also	O
used	O
on	O
video	B-Protocol
game	I-Protocol
cartridges	I-Protocol
to	O
save	O
game	O
progress	O
and	O
configurations	O
,	O
before	O
the	O
usage	O
of	O
external	O
and	O
internal	O
flash	B-Device
memories	I-Device
.	O
</s>
<s>
During	O
rewrites	O
,	O
the	O
gate	O
oxide	O
in	O
the	O
floating-gate	B-Algorithm
transistors	I-Algorithm
gradually	O
accumulates	O
trapped	O
electrons	O
.	O
</s>
<s>
The	O
electric	O
field	O
of	O
the	O
trapped	O
electrons	O
adds	O
to	O
the	O
electrons	O
in	O
the	O
floating	B-Algorithm
gate	I-Algorithm
,	O
lowering	O
the	O
window	O
between	O
threshold	O
voltages	O
for	O
zeros	O
vs	O
ones	O
.	O
</s>
<s>
During	O
storage	O
,	O
the	O
electrons	O
injected	O
into	O
the	O
floating	B-Algorithm
gate	I-Algorithm
may	O
drift	O
through	O
the	O
insulator	O
,	O
especially	O
at	O
increased	O
temperature	O
,	O
and	O
cause	O
charge	O
loss	O
,	O
reverting	O
the	O
cell	O
into	O
erased	O
state	O
.	O
</s>
<s>
Flash	B-Device
memory	I-Device
is	O
a	O
later	O
form	O
of	O
EEPROM	B-General_Concept
.	O
</s>
<s>
In	O
the	O
industry	O
,	O
there	O
is	O
a	O
convention	O
to	O
reserve	O
the	O
term	O
EEPROM	B-General_Concept
to	O
byte-wise	O
erasable	O
memories	O
compared	O
to	O
block-wise	O
erasable	O
flash	B-Device
memories	I-Device
.	O
</s>
<s>
EEPROM	B-General_Concept
occupies	O
more	O
die	O
area	O
than	O
flash	B-Device
memory	I-Device
for	O
the	O
same	O
capacity	O
,	O
because	O
each	O
cell	O
usually	O
needs	O
a	O
read	O
,	O
a	O
write	O
,	O
and	O
an	O
erase	O
transistor	B-Application
,	O
while	O
flash	B-Device
memory	I-Device
erase	O
circuits	O
are	O
shared	O
by	O
large	O
blocks	O
of	O
cells	O
(	O
often	O
512×8	O
)	O
.	O
</s>
<s>
Newer	O
non-volatile	B-General_Concept
memory	I-General_Concept
technologies	O
such	O
as	O
FeRAM	O
and	O
MRAM	B-General_Concept
are	O
slowly	O
replacing	O
EEPROMs	B-General_Concept
in	O
some	O
applications	O
,	O
but	O
are	O
expected	O
to	O
remain	O
a	O
small	O
fraction	O
of	O
the	O
EEPROM	B-General_Concept
market	O
for	O
the	O
foreseeable	O
future	O
.	O
</s>
<s>
The	O
difference	O
between	O
EPROM	B-General_Concept
and	O
EEPROM	B-General_Concept
lies	O
in	O
the	O
way	O
that	O
the	O
memory	O
programs	O
and	O
erases	O
.	O
</s>
<s>
EEPROM	B-General_Concept
can	O
be	O
programmed	O
and	O
erased	O
electrically	O
using	O
field	O
electron	O
emission	O
(	O
more	O
commonly	O
known	O
in	O
the	O
industry	O
as	O
"	O
Fowler	O
–	O
Nordheim	O
tunneling	O
"	O
)	O
.	O
</s>
<s>
EPROMs	B-General_Concept
ca	O
n't	O
be	O
erased	O
electrically	O
and	O
are	O
programmed	O
by	O
hot-carrier	O
injection	O
onto	O
the	O
floating	B-Algorithm
gate	I-Algorithm
.	O
</s>
<s>
Erase	O
is	O
by	O
an	O
ultraviolet	B-Application
light	O
source	O
,	O
although	O
in	O
practice	O
many	O
EPROMs	B-General_Concept
are	O
encapsulated	O
in	O
plastic	O
that	O
is	O
opaque	O
to	O
UV	O
light	O
,	O
making	O
them	O
"	O
one-time	O
programmable	O
"	O
.	O
</s>
<s>
Most	O
NOR	O
flash	B-Device
memory	I-Device
is	O
a	O
hybrid	O
style	O
—	O
programming	O
is	O
through	O
hot-carrier	O
injection	O
and	O
erase	O
is	O
through	O
Fowler	O
–	O
Nordheim	O
tunneling	O
.	O
</s>
