<s>
POKEY	B-Device
,	O
an	O
acronym	O
for	O
Pot	B-Device
Keyboard	I-Device
Integrated	I-Device
Circuit	I-Device
,	O
is	O
a	O
digital	O
I/O	B-General_Concept
chip	B-Architecture
designed	O
by	O
Doug	O
Neubauer	O
at	O
Atari	O
,	O
Inc	O
.	O
for	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
of	O
home	O
computers	O
.	O
</s>
<s>
It	O
was	O
first	O
released	O
with	O
the	O
Atari	O
400	O
and	O
Atari	B-Device
800	I-Device
in	O
1979	O
and	O
is	O
included	O
in	O
all	O
later	O
models	O
and	O
the	O
Atari	B-General_Concept
5200	I-General_Concept
console	O
.	O
</s>
<s>
POKEY	B-Device
combines	O
functions	O
for	O
reading	O
paddle	B-Device
controllers	I-Device
(	O
potentiometers	B-Device
)	O
and	O
computer	B-Device
keyboards	I-Device
as	O
well	O
as	O
sound	O
generation	O
and	O
a	O
source	O
for	O
pseudorandom	B-Algorithm
numbers	I-Algorithm
.	O
</s>
<s>
Neubauer	O
also	O
developed	O
the	O
Atari	B-Device
8-bit	I-Device
killer	O
application	O
Star	B-Application
Raiders	I-Application
which	O
makes	O
use	O
of	O
POKEY	B-Device
features	O
.	O
</s>
<s>
POKEY	B-Device
chips	O
are	O
used	O
for	O
audio	O
in	O
many	O
arcade	O
video	O
games	O
of	O
the	O
1980s	O
including	O
Centipede	B-Application
,	O
Missile	B-Application
Command	I-Application
,	O
Asteroids	B-Application
Deluxe	I-Application
,	O
and	O
Gauntlet	B-Device
.	O
</s>
<s>
Some	O
of	O
Atari	B-Application
's	I-Application
arcade	I-Application
systems	I-Application
use	O
multi-core	O
versions	O
with	O
2	O
or	O
4	O
POKEYs	B-Device
in	O
a	O
single	O
package	O
for	O
more	O
audio	O
channels	O
.	O
</s>
<s>
The	O
Atari	B-General_Concept
7800	I-General_Concept
console	O
allows	O
a	O
game	O
cartridge	O
to	O
contain	O
a	O
POKEY	B-Device
,	O
providing	O
better	O
sound	O
than	O
the	O
system	O
's	O
audio	O
chip	B-Architecture
.	O
</s>
<s>
Only	O
two	O
licensed	O
games	O
make	O
use	O
of	O
this	O
:	O
the	O
ports	O
of	O
Ballblazer	B-Application
and	O
Commando	B-Application
.	O
</s>
<s>
The	O
LSI	O
chip	B-Architecture
has	O
40	O
pins	O
and	O
is	O
identified	O
as	O
C012294	B-Device
.	O
</s>
<s>
No	O
longer	O
manufactured	O
,	O
POKEY	B-Device
is	O
emulated	O
in	O
software	O
by	O
arcade	O
and	O
Atari	B-Device
8-bit	I-Device
emulators	O
and	O
also	O
via	O
the	O
Atari	O
SAP	O
music	O
format	O
and	O
associated	O
player	O
.	O
</s>
<s>
C012294	B-Device
Used	O
in	O
all	O
Atari	B-Device
8-bit	I-Device
family	I-Device
computers	O
,	O
including	O
the	O
Atari	B-General_Concept
XEGS	I-General_Concept
,	O
as	O
well	O
as	O
the	O
Atari	B-General_Concept
5200	I-General_Concept
console	O
.	O
</s>
<s>
The	O
suffix	O
on	O
the	O
chip	B-Architecture
refers	O
to	O
the	O
manufacturer	O
:	O
</s>
<s>
137430-001	O
Part	O
number	O
sometimes	O
used	O
in	O
Atari	O
arcade	O
machines	O
for	O
POKEY	B-Device
.	O
</s>
<s>
137324-1221	O
Quad-Core	O
POKEY	B-Device
used	O
in	O
Atari	O
arcade	O
machines	O
Major	B-Application
Havoc	I-Application
,	O
I	B-Application
,	I-Application
Robot	I-Application
,	O
Firefox	B-Application
,	O
and	O
Return	B-Application
of	I-Application
the	I-Application
Jedi	I-Application
.	O
</s>
<s>
The	O
Atari	B-Device
8-bit	I-Device
computers	I-Device
map	O
POKEY	B-Device
to	O
the	O
$D2xxhex	O
page	O
and	O
the	O
Atari	B-General_Concept
5200	I-General_Concept
console	O
maps	O
it	O
to	O
the	O
$E8xxhex	O
page	O
.	O
</s>
<s>
POKEY	B-Device
provides	O
29	O
Read/Write	O
registers	O
controlling	O
Sound	O
,	O
Paddle	B-Device
input	O
,	O
keyboard	B-Device
input	O
,	O
serial	B-Protocol
input/output	B-General_Concept
,	O
and	O
interrupts	O
.	O
</s>
<s>
Many	O
POKEY	B-Device
register	O
addresses	O
have	O
dual	O
purposes	O
performing	O
different	O
functions	O
as	O
a	O
Read	O
vs	O
a	O
Write	O
register	O
.	O
</s>
<s>
Reading	O
values	O
directly	O
from	O
hardware	O
at	O
an	O
unknown	O
stage	O
in	O
the	O
display	O
cycle	O
may	O
return	O
inconsistent	O
results	O
(	O
an	O
example	O
:	O
reading	O
potentiometers	B-Device
)	O
.	O
</s>
<s>
Pokey	B-Device
contains	O
a	O
programmable	O
sound	O
generator	O
;	O
four	O
audio	O
channels	O
with	O
separate	O
frequency	O
,	O
noise	O
and	O
voice	O
level	O
controls	O
.	O
</s>
<s>
Each	O
channel	O
has	O
an	O
8-bit	O
frequency	O
divider	O
and	O
an	O
8-bit	O
register	O
to	O
select	O
noise	O
and	O
volume	B-Algorithm
.	O
</s>
<s>
POKEY	B-Device
's	O
sound	O
is	O
distinctive	O
:	O
when	O
the	O
four	O
channels	O
are	O
used	O
independently	O
,	O
there	O
is	O
noticeable	O
detuning	O
of	O
parts	O
of	O
the	O
12-tone	O
equal	O
temperament	O
scale	O
,	O
due	O
to	O
lack	O
of	O
pitch	O
accuracy	O
.	O
</s>
<s>
One	O
of	O
the	O
sound-engines	O
developed	O
for	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
was	O
called	O
the	O
AMP	O
engine	O
(	O
Advanced	O
Music	O
Processor	O
)	O
.	O
</s>
<s>
This	O
was	O
used	O
by	O
the	O
musician	O
Gary	B-Application
Gilbertson	I-Application
.	O
</s>
<s>
The	O
AUDF*	O
values	O
also	O
control	O
the	O
POKEY	B-Device
hardware	O
timers	O
useful	O
for	O
code	O
that	O
must	O
run	O
in	O
precise	O
intervals	O
more	O
frequent	O
than	O
the	O
vertical	O
blank	O
.	O
</s>
<s>
Each	O
AUDF*	O
register	O
is	O
an	O
8-bit	O
value	O
providing	O
a	O
countdown	O
timer	O
or	O
divisor	O
for	O
the	O
pulses	O
from	O
the	O
POKEY	B-Device
clock	O
.	O
</s>
<s>
So	O
,	O
smaller	O
values	O
permit	O
more	O
frequent	O
output	O
of	O
pulses	O
from	O
POKEY	B-Device
,	O
and	O
larger	O
values	O
,	O
less	O
frequent	O
.	O
</s>
<s>
The	O
values	O
$	O
0hex/0dec	O
to	O
$	O
FFhex/255dec	O
are	O
incremented	O
by	O
POKEY	B-Device
to	O
range	O
from	O
$	O
1hex/1dec	O
to	O
$	O
100hex/256dec	O
.	O
</s>
<s>
The	O
actual	O
audible	O
sound	O
pitch	O
is	O
dependent	O
on	O
the	O
POKEY	B-Device
clock	O
frequency	O
and	O
distortion	O
values	O
chosen	O
.	O
</s>
<s>
The	O
Audio	O
Channel	O
control	O
registers	O
provide	O
volume	B-Algorithm
and	O
distortion	O
control	O
over	O
individual	O
sound	O
channels	O
.	O
</s>
<s>
Audio	O
may	O
also	O
be	O
generated	O
independently	O
of	O
the	O
POKEY	B-Device
clock	O
by	O
direct	O
volume	B-Algorithm
manipulation	O
of	O
a	O
sound	O
channel	O
which	O
is	O
useful	O
for	O
playing	O
back	O
digital	O
samples	O
.	O
</s>
<s>
Bit	O
0-3	O
:	O
Control	O
over	O
volume	B-Algorithm
level	O
,	O
from	O
0	O
to	O
F	O
.	O
</s>
<s>
Bit	O
4	O
:	O
Forced	O
volume-only	O
output	O
.	O
</s>
<s>
Sound	O
is	O
produced	O
only	O
by	O
setting	O
volume	B-Algorithm
bits	O
0:3	O
.	O
</s>
<s>
This	O
feature	O
was	O
used	O
to	O
create	O
digital	O
audio	O
via	O
pulse-code	B-Algorithm
modulation	I-Algorithm
.	O
</s>
<s>
In	O
this	O
way	O
,	O
POKEY	B-Device
makes	O
possible	O
connecting	O
of	O
8-bit	O
channels	O
to	O
create	O
sound	O
with	O
16-bit	O
accuracy	O
.	O
</s>
<s>
POKEY	B-Device
has	O
eight	O
analog	O
to	O
digital	O
converter	O
ports	O
most	O
commonly	O
used	O
for	O
potentiometers	B-Device
,	O
also	O
known	O
as	O
Paddle	B-Device
Controllers	I-Device
.	O
</s>
<s>
The	O
analog	O
inputs	O
are	O
also	O
used	O
for	O
the	O
Touch	O
Tablet	O
controller	O
,	O
and	O
the	O
12-button	O
,	O
video	O
game	O
Keyboard	B-Device
Controllers	O
.	O
</s>
<s>
The	O
timers	O
can	O
also	O
be	O
used	O
to	O
support	O
a	O
light	B-Device
pen	I-Device
,	O
by	O
connecting	O
a	O
photodiode	O
to	O
the	O
drop	O
transistor	O
,	O
which	O
captures	O
the	O
timer	O
when	O
the	O
electron	O
beam	O
in	O
the	O
television	O
passes	O
by	O
the	O
pen	O
.	O
</s>
<s>
This	O
had	O
the	O
added	O
advantage	O
of	O
allowing	O
the	O
value	O
read	O
out	O
to	O
be	O
fed	O
directly	O
into	O
screen	O
coordinates	O
of	O
objects	O
being	O
driven	O
by	O
the	O
paddles	B-Device
.	O
</s>
<s>
The	O
Atari	B-Device
Paddle	I-Device
values	O
range	O
from	O
0	O
to	O
228	O
,	O
though	O
the	O
maximum	O
possible	O
is	O
244	O
.	O
</s>
<s>
The	O
Paddle	B-Device
controller	I-Device
reads	O
0	O
when	O
turned	O
to	O
its	O
maximum	O
clockwise	O
position	O
,	O
and	O
returns	O
increasing	O
values	O
as	O
it	O
is	O
turned	O
counter-clockwise	O
ending	O
at	O
its	O
maximum	O
value	O
.	O
</s>
<s>
The	O
Paddle	B-Device
reading	O
process	O
begins	O
by	O
writing	O
to	O
POTGO	O
which	O
resets	O
the	O
POT*	O
values	O
to	O
0	O
,	O
the	O
ALLPOT	O
value	O
to	O
$FF	O
,	O
and	O
discharges	O
the	O
potentiometer	B-Device
read	O
capacitors	O
.	O
</s>
<s>
The	O
POT*	O
values	O
increment	O
as	O
they	O
are	O
being	O
scanned	O
until	O
reaching	O
the	O
resistance	O
value	O
of	O
the	O
potentiometer	B-Device
.	O
</s>
<s>
When	O
the	O
Paddle	B-Device
reading	O
is	O
complete	O
the	O
corresponding	O
bit	O
in	O
ALLPOT	O
is	O
reset	O
to	O
0	O
.	O
</s>
<s>
The	O
Paddle	B-Device
scanning	O
process	O
can	O
take	O
the	O
majority	O
of	O
a	O
video	O
frame	O
to	O
complete	O
.	O
</s>
<s>
The	O
Atari	O
Operating	O
System	O
takes	O
care	O
of	O
Paddle	B-Device
reading	O
automatically	O
.	O
</s>
<s>
The	O
Paddles	B-Device
are	O
read	O
and	O
paddle	B-Device
scanning	O
initiated	O
during	O
the	O
stage	O
2	O
vertical	O
blank	O
.	O
</s>
<s>
Paddle	B-Device
values	O
are	O
copied	O
to	O
shadow	O
registers	O
.	O
</s>
<s>
(	O
Note	O
that	O
Paddle	B-Device
triggers	O
are	O
actually	O
joystick	O
direction	O
input	O
read	O
from	O
PIA	O
.	O
)	O
</s>
<s>
A	O
faster	O
mode	O
of	O
scanning	O
the	O
Paddles	B-Device
is	O
possible	O
by	O
setting	O
a	O
bit	O
in	O
SKCTL	O
.	O
</s>
<s>
Each	O
bit	O
corresponds	O
to	O
one	O
potentiometer	B-Device
input	O
(	O
the	O
POT*	O
registers	O
)	O
.	O
</s>
<s>
When	O
paddle	B-Device
scanning	O
is	O
started	O
by	O
writing	O
to	O
POTGO	O
each	O
paddle	B-Device
's	O
bit	O
in	O
ALLPOT	O
is	O
set	O
to	O
1	O
.	O
</s>
<s>
When	O
a	O
paddle	B-Device
's	O
scan	O
is	O
complete	O
the	O
corresponding	O
bit	O
in	O
ALLPOT	O
is	O
reset	O
to	O
0	O
indicating	O
the	O
value	O
in	O
the	O
associated	O
POT*	O
register	O
is	O
now	O
valid	O
to	O
read	O
.	O
</s>
<s>
Writing	O
to	O
POTGO	O
initiates	O
the	O
potentiometer	B-Device
(	O
Paddle	B-Device
)	O
scanning	O
process	O
.	O
</s>
<s>
This	O
resets	O
the	O
POT*	O
values	O
to	O
0	O
,	O
the	O
ALLPOT	O
value	O
to	O
$FF	O
,	O
and	O
discharges	O
the	O
potentiometer	B-Device
read	O
capacitors	O
.	O
</s>
<s>
As	O
each	O
potentiometer	B-Device
scan	O
completes	O
the	O
bit	O
corresponding	O
to	O
the	O
potentiometer	B-Device
in	O
ALLPOT	O
is	O
cleared	O
indicating	O
the	O
value	O
of	O
the	O
associated	O
POT*	O
register	O
is	O
valid	O
for	O
reading	O
.	O
</s>
<s>
POKEY	B-Device
is	O
a	O
sort	O
of	O
UART	O
.	O
</s>
<s>
A	O
byte	O
put	O
into	O
the	O
SEROUT	O
register	O
is	O
automatically	O
sent	O
over	O
the	O
serial	B-Protocol
bus	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
connect	O
the	O
Atari	O
serial	B-Protocol
port	O
with	O
an	O
RS-232	O
port	O
by	O
means	O
of	O
a	O
simple	O
voltage	O
converter	O
.	O
</s>
<s>
Each	O
input/output	B-General_Concept
operation	O
causes	O
POKEY	B-Device
's	O
internal	O
shift	O
registers	O
to	O
change	O
value	O
,	O
so	O
when	O
programming	O
for	O
POKEY	B-Device
,	O
it	O
is	O
necessary	O
to	O
re-initialise	O
some	O
values	O
after	O
each	O
operation	O
is	O
carried	O
out	O
.	O
</s>
<s>
Reset	O
Serial	B-Protocol
Port	O
Status	O
(	O
SKSTAT	O
)	O
.	O
</s>
<s>
The	O
latches	O
flag	O
keyboard	B-Device
overrun	O
,	O
Serial	B-Protocol
data	O
input	O
overrun	O
,	O
and	O
Serial	B-Protocol
data	O
input	O
frame	O
error	O
.	O
</s>
<s>
Serial	B-Protocol
port	O
data	O
output	O
byte	O
.	O
</s>
<s>
This	O
is	O
a	O
parallel	O
"	O
holding	O
"	O
register	O
for	O
the	O
eight	O
bit	O
(	O
one	O
byte	O
)	O
value	O
that	O
will	O
be	O
transferred	O
to	O
the	O
serial	B-Protocol
shift	O
register	O
for	O
output	O
one	O
bit	O
at	O
a	O
time	O
.	O
</s>
<s>
When	O
the	O
port	O
is	O
ready	O
to	O
accept	O
data	O
for	O
output	O
a	O
Serial	B-Protocol
Data	O
Out	O
interrupt	O
informs	O
the	O
Operating	O
System	O
that	O
it	O
can	O
write	O
a	O
byte	O
to	O
this	O
output	O
register	O
.	O
</s>
<s>
Serial	B-Protocol
port	O
data	O
input	O
byte	O
.	O
</s>
<s>
This	O
holds	O
the	O
eight	O
bit	O
(	O
one	O
byte	O
)	O
value	O
assembled	O
by	O
the	O
serial	B-Protocol
shift	O
register	O
reading	O
the	O
data	O
input	O
one	O
bit	O
at	O
a	O
time	O
.	O
</s>
<s>
When	O
a	O
full	O
byte	O
is	O
read	O
a	O
Serial	B-Protocol
Data	O
In	O
interrupt	O
occurs	O
informing	O
the	O
Operating	O
System	O
that	O
it	O
can	O
read	O
the	O
byte	O
from	O
this	O
register	O
.	O
</s>
<s>
A	O
value	O
of	O
1	O
enables	O
POKEY	B-Device
to	O
use	O
an	O
internal	O
comparison	O
register	O
while	O
scanning	O
keys	O
.	O
</s>
<s>
This	O
should	O
be	O
enabled	O
to	O
maintain	O
normal	O
keyboard	B-Device
handling	O
with	O
the	O
Operating	O
System	O
.	O
</s>
<s>
Bit	O
1	O
:	O
Set	O
to	O
1	O
to	O
enable	O
keyboard	B-Device
scanning	O
.	O
</s>
<s>
This	O
should	O
be	O
enabled	O
to	O
maintain	O
normal	O
keyboard	B-Device
handling	O
with	O
the	O
Operating	O
System	O
.	O
</s>
<s>
Bit	O
2	O
:	O
Set	O
to	O
1	O
to	O
enable	O
fast	O
,	O
though	O
less	O
accurate	O
Potentiometer	B-Device
scanning	O
.	O
</s>
<s>
The	O
OS	O
reads	O
the	O
Pot	O
values	O
during	O
its	O
Vertical	O
Blank	O
Interrupt	O
(	O
VBI	O
)	O
and	O
copies	O
the	O
result	O
to	O
the	O
potentiometer	B-Device
Shadow	O
registers	O
in	O
RAM	O
.	O
</s>
<s>
Bit	O
3	O
:	O
Enable	O
Serial	B-Protocol
port	O
two-tone	O
mode	O
.	O
</s>
<s>
Bit	O
4-6	O
:	O
Clock	O
Timing	O
Control	O
for	O
serial	B-Protocol
port	O
operation	O
.	O
</s>
<s>
Bit	O
7	O
:	O
Forces	O
a	O
known	O
0	O
output	O
,	O
so	O
that	O
timer	O
2	O
can	O
reset	O
timer	O
1	O
in	O
two-tone	O
serial	B-Protocol
output	O
mode	O
.	O
</s>
