<s>
The	O
Hitachi	B-Device
HD44780	I-Device
LCD	I-Device
controller	I-Device
is	O
an	O
alphanumeric	O
dot	B-General_Concept
matrix	I-General_Concept
liquid	B-Device
crystal	I-Device
display	I-Device
(	O
LCD	B-Device
)	O
controller	O
developed	O
by	O
Hitachi	O
in	O
the	O
1980s	O
.	O
</s>
<s>
The	O
character	O
set	O
of	O
the	O
controller	O
includes	O
ASCII	B-Protocol
characters	I-Protocol
,	O
Japanese	O
Kana	O
characters	O
,	O
and	O
some	O
symbols	O
in	O
two	O
40	O
character	O
lines	O
.	O
</s>
<s>
Numerous	O
third-party	O
displays	O
are	O
compatible	O
with	O
its	O
16-pin	O
interface	O
and	O
instruction	O
set	O
,	O
making	O
it	O
a	O
popular	O
and	O
cheap	O
LCD	B-Device
driver	O
.	O
</s>
<s>
The	O
Hitachi	B-Device
HD44780	I-Device
LCD	I-Device
controller	I-Device
is	O
limited	O
to	O
monochrome	O
text	O
displays	O
and	O
is	O
often	O
used	O
in	O
copiers	O
,	O
fax	O
machines	O
,	O
laser	O
printers	O
,	O
industrial	O
test	O
equipment	O
,	O
and	O
networking	O
equipment	O
,	O
such	O
as	O
routers	B-Protocol
and	O
storage	O
devices	O
.	O
</s>
<s>
Compatible	O
LCD	B-Device
screens	I-Device
are	O
manufactured	O
in	O
several	O
standard	O
configurations	O
.	O
</s>
<s>
Character	O
LCDs	B-Device
may	O
have	O
a	O
backlight	O
,	O
which	O
may	O
be	O
LED	O
,	O
fluorescent	O
,	O
or	O
electroluminescent	O
.	O
</s>
<s>
Character	O
LCDs	B-Device
use	O
a	O
16-contact	O
interface	O
,	O
commonly	O
using	O
pins	B-Protocol
or	O
card	O
edge	O
connections	O
on	O
0.1inch	O
(	O
2.54mm	O
)	O
centers	O
.	O
</s>
<s>
Those	O
without	O
backlights	O
may	O
have	O
only	O
14	O
pins	B-Protocol
,	O
omitting	O
the	O
two	O
pins	B-Protocol
powering	O
the	O
light	O
.	O
</s>
<s>
This	O
interface	O
was	O
designed	O
to	O
be	O
easily	O
hooked	O
up	O
to	O
the	O
Intel	B-Architecture
MCS-51	I-Architecture
XRAM	O
interface	O
,	O
using	O
only	O
two	O
address	O
pins	B-Protocol
,	O
which	O
allowed	O
displaying	O
text	O
on	O
LCD	B-Device
using	O
simple	O
MOVX	O
commands	O
,	O
offering	O
cost	O
effective	O
option	O
for	O
adding	O
text	O
display	O
to	O
devices	O
.	O
</s>
<s>
In	O
that	O
case	O
,	O
this	O
pin	O
can	O
be	O
permanently	O
connected	O
to	O
ground	O
and	O
no	O
processor	O
pins	B-Protocol
need	O
to	O
be	O
allocated	O
to	O
control	O
it	O
.	O
</s>
<s>
In	O
8-bit	O
mode	O
,	O
all	O
transfers	O
happen	O
in	O
one	O
cycle	O
of	O
the	O
enable	O
pin	O
(	O
E	O
)	O
with	O
all	O
8	O
bits	O
on	O
the	O
data	O
bus	O
and	O
the	O
RS	O
and	O
R/	O
pins	B-Protocol
stable	O
.	O
</s>
<s>
In	O
4-bit	O
mode	O
,	O
data	O
are	O
transferred	O
as	O
pairs	O
of	O
4-bit	O
"	O
nibbles	O
"	O
on	O
the	O
upper	O
data	O
pins	B-Protocol
,	O
D7	O
–	O
D4	O
,	O
with	O
two	O
enable	O
pulses	O
and	O
the	O
RS	O
and	O
R/	O
pins	B-Protocol
stable	O
.	O
</s>
<s>
First	O
,	O
with	O
D3	O
–	O
D0	O
unconnected	O
,	O
these	O
lines	O
will	O
always	O
appear	O
high	O
(	O
binary	O
1111	O
)	O
to	O
the	O
HD44780	O
since	O
there	O
are	O
internal	O
pull-up	O
MOSFETs	B-Architecture
.	O
</s>
<s>
Second	O
,	O
the	O
LCD	B-Device
may	O
initially	O
be	O
in	O
one	O
of	O
three	O
states	O
:	O
</s>
<s>
The	O
following	O
algorithm	O
ensures	O
that	O
the	O
LCD	B-Device
is	O
in	O
the	O
desired	O
mode	O
:	O
</s>
<s>
The	O
original	O
HD44780	O
character	O
generator	O
ROM	O
contains	O
208	O
characters	O
in	O
a	O
5×8	O
dot	B-General_Concept
matrix	I-General_Concept
,	O
and	O
32	O
characters	O
in	O
a	O
5×10	O
dot	B-General_Concept
matrix	I-General_Concept
.	O
</s>
<s>
The	O
7-bit	B-Protocol
ASCII	I-Protocol
subset	O
for	O
the	O
Japanese	O
version	O
is	O
non-standard	O
:	O
it	O
supplies	O
a	O
Yen	O
symbol	O
where	O
the	O
backslash	O
character	O
is	O
normally	O
found	O
,	O
and	O
left	O
and	O
right	O
arrow	O
symbols	O
in	O
place	O
of	O
tilde	O
and	O
the	O
rubout	O
character	O
.	O
</s>
<s>
These	O
characters	O
have	O
to	O
be	O
written	O
to	O
the	O
device	O
each	O
time	O
it	O
is	O
switched	O
on	O
,	O
as	O
they	O
are	O
stored	O
in	O
volatile	B-General_Concept
memory	I-General_Concept
.	O
</s>
