<s>
The	O
6551	B-Architecture
Asynchronous	B-Architecture
Communications	I-Architecture
Interface	I-Architecture
Adapter	I-Architecture
(	O
ACIA	O
)	O
is	O
an	O
integrated	O
circuit	O
made	O
by	O
MOS	B-Architecture
Technology	I-Architecture
.	O
</s>
<s>
It	O
served	O
as	O
a	O
companion	O
UART	O
chip	O
for	O
the	O
widely	O
popular	O
6502	B-General_Concept
microprocessor	I-General_Concept
.	O
</s>
<s>
The	O
6551	B-Architecture
was	O
used	O
in	O
several	O
computers	O
of	O
the	O
1970s	O
and	O
1980s	O
,	O
including	O
the	O
Commodore	B-Device
PET	I-Device
and	O
Plus/4	B-Operating_System
.	O
</s>
<s>
It	O
was	O
also	O
used	O
by	O
Apple	O
Computer	O
on	O
the	O
Apple	O
II	O
Super	O
Serial	O
Card	O
,	O
and	O
by	O
Radio	O
Shack	O
on	O
the	O
Deluxe	O
RS-232	O
Program	O
Pak	O
for	O
their	O
TRS-80	B-Device
Color	I-Device
Computer	I-Device
.	O
</s>
<s>
Evil	O
Labs	O
and	O
Creative	O
Micro	O
Designs	O
,	O
marketed	O
an	O
add-on	O
cartridge	B-Protocol
containing	O
a	O
6551	B-Architecture
and	O
an	O
industry-standard	O
RS-232	O
port	O
to	O
allow	O
the	O
C64	O
and	O
128	O
to	O
use	O
high-speed	O
modems	O
from	O
companies	O
such	O
as	O
U.S.	O
Robotics	O
and	O
Hayes	O
Communications	O
.	O
</s>
<s>
Evil	O
and	O
CMD	O
cartridges	B-Protocol
pushed	O
the	O
6551	B-Architecture
to	O
38,400	O
baud	O
and	O
,	O
with	O
a	O
faster-still	O
clock	O
crystal	O
,	O
some	O
end	O
users	O
reported	O
getting	O
115,200	O
bit/s	O
from	O
the	O
6551	B-Architecture
.	O
</s>
<s>
The	O
ADTPro	O
file	O
transfer	O
program	O
disables	O
the	O
baud	O
rate	O
generator	O
in	O
the	O
6551	B-Architecture
,	O
allowing	O
115,200	O
bit/s	O
transfers	O
with	O
an	O
unmodified	O
clock	O
crystal	O
.	O
</s>
<s>
The	O
Rockwell	O
65C52	O
combines	O
two	O
CMOS	B-Device
6551s	B-Architecture
on	O
a	O
chip	O
.	O
</s>
<s>
The	O
Motorola	O
6850	O
is	O
a	O
similar	O
chip	O
to	O
the	O
MOS	B-Architecture
Technology	I-Architecture
6551	I-Architecture
.	O
</s>
<s>
The	O
Western	B-Application
Design	I-Application
Center	I-Application
WDC	I-Application
65C51	I-Application
is	O
designed	O
as	O
a	O
drop	O
in	O
replacement	O
for	O
the	O
original	O
MOS	B-Architecture
6551	I-Architecture
,	O
electrically	O
,	O
physically	O
and	O
programming	O
-	O
compatible	O
with	O
most	O
6551	B-Architecture
and	O
6850	O
derivatives	O
from	O
most	O
other	O
suppliers	O
.	O
</s>
