<s>
The	O
Electronic	B-General_Concept
Arrays	I-General_Concept
9002	I-General_Concept
,	O
or	O
EA9002	B-General_Concept
,	O
was	O
an	O
8-bit	O
microprocessor	O
released	O
in	O
1976	O
.	O
</s>
<s>
It	O
included	O
64	O
bytes	O
of	O
built-in	O
RAM	B-Architecture
and	O
could	O
be	O
directly	O
connected	O
to	O
TTL	B-General_Concept
devices	O
.	O
</s>
<s>
It	O
was	O
packaged	O
in	O
a	O
28-pin	O
DIP	B-Algorithm
which	O
made	O
it	O
less	O
expensive	O
to	O
implement	O
than	O
contemporary	O
designs	O
like	O
the	O
40-pin	O
MOS	B-General_Concept
6502	I-General_Concept
and	O
Zilog	B-General_Concept
Z80	I-General_Concept
.	O
</s>
<s>
Today	O
it	O
would	O
be	O
known	O
as	O
a	O
microcontroller	B-Architecture
,	O
although	O
that	O
term	O
did	O
not	O
exist	O
at	O
the	O
time	O
.	O
</s>
<s>
This	O
was	O
not	O
a	O
significant	O
limitation	O
at	O
the	O
time	O
,	O
as	O
memory	O
was	O
still	O
very	O
expensive	O
and	O
the	O
target	O
market	O
could	O
often	O
make	O
do	O
with	O
the	O
internal	O
RAM	B-Architecture
.	O
</s>
<s>
Electronic	O
Arrays	O
(	O
EA	O
)	O
had	O
problems	O
with	O
the	O
new	O
depletion-load	B-Algorithm
NMOS	I-Algorithm
logic	I-Algorithm
fabrication	O
line	O
and	O
struggled	O
with	O
deliveries	O
.	O
</s>
<s>
By	O
1977	O
,	O
the	O
6502	B-General_Concept
and	O
Z80	B-General_Concept
had	O
taken	O
over	O
much	O
of	O
the	O
market	O
,	O
and	O
in	O
November	O
EA	O
stopped	O
selling	O
the	O
design	O
.	O
</s>
<s>
At	O
the	O
time	O
the	O
9002	O
was	O
designed	O
,	O
the	O
microcomputer	B-Architecture
had	O
not	O
yet	O
emerged	O
as	O
a	O
major	O
market	O
and	O
processors	O
of	O
the	O
era	O
were	O
mostly	O
used	O
in	O
embedded	O
electronics	O
like	O
electronic	O
calculators	O
,	O
cash	O
registers	O
,	O
gas	O
pumps	O
,	O
and	O
similar	O
roles	O
.	O
</s>
<s>
For	O
these	O
uses	O
,	O
the	O
computer	B-Application
program	I-Application
was	O
normally	O
stored	O
on	O
read-only	B-Device
memory	I-Device
(	O
ROM	B-Device
)	O
and	O
the	O
amount	O
of	O
random-access	B-Architecture
memory	I-Architecture
(	O
RAM	B-Architecture
)	O
needed	O
was	O
very	O
small	O
–	O
keeping	O
track	O
of	O
the	O
number	O
of	O
gallons	O
pumped	O
and	O
the	O
total	O
cost	O
for	O
instance	O
.	O
</s>
<s>
In	O
the	O
mid-1970s	O
,	O
dynamic	O
RAM	B-Architecture
had	O
not	O
yet	O
emerged	O
as	O
the	O
primary	O
form	O
of	O
main	O
memory	O
,	O
and	O
most	O
systems	O
used	O
the	O
much	O
more	O
expensive	O
static	B-Architecture
RAM	I-Architecture
.	O
</s>
<s>
For	O
embedded	O
controllers	O
,	O
this	O
could	O
represent	O
a	O
significant	O
cost	O
,	O
so	O
it	O
was	O
desirable	O
for	O
designers	O
to	O
add	O
a	O
small	O
amount	O
of	O
"	O
scratchpad	O
RAM	B-Architecture
"	O
to	O
the	O
system	O
to	O
avoid	O
having	O
to	O
add	O
additional	O
RAM	B-Architecture
chips	I-Architecture
to	O
the	O
board	O
.	O
</s>
<s>
As	O
most	O
systems	O
would	O
have	O
little	O
or	O
no	O
external	O
RAM	B-Architecture
and	O
small	O
programs	O
in	O
ROM	B-Device
,	O
it	O
was	O
also	O
common	O
to	O
use	O
smaller	O
address	B-General_Concept
spaces	I-General_Concept
as	O
this	O
allowed	O
the	O
number	O
of	O
pins	O
to	O
be	O
reduced	O
,	O
which	O
simplified	O
circuit	O
board	O
layout	O
.	O
</s>
<s>
Another	O
major	O
change	O
taking	O
place	O
in	O
the	O
mid-1970s	O
was	O
the	O
introduction	O
of	O
depletion-load	B-Algorithm
NMOS	I-Algorithm
logic	I-Algorithm
design	O
.	O
</s>
<s>
This	O
not	O
only	O
made	O
the	O
circuit	O
layout	O
more	O
complex	O
and	O
often	O
required	O
a	O
more	O
complex	O
power	O
supply	O
as	O
well	O
,	O
it	O
also	O
made	O
it	O
more	O
difficult	O
to	O
interface	O
with	O
external	O
support	O
circuits	O
which	O
were	O
mostly	O
based	O
on	O
transistor-transistor	B-General_Concept
logic	I-General_Concept
(	O
TTL	B-General_Concept
)	O
which	O
ran	O
at	O
+5V	O
.	O
</s>
<s>
Interfacing	O
older	O
chips	O
with	O
the	O
wide	O
variety	O
of	O
TTL	B-General_Concept
components	O
generally	O
required	O
additional	O
latches	B-General_Concept
,	O
but	O
the	O
new	O
depletion-load	O
designs	O
worked	O
at	O
+5V	O
and	O
interfaced	O
directly	O
,	O
reducing	O
cost	O
and	O
complexity	O
.	O
</s>
<s>
It	O
included	O
64	O
bytes	O
of	O
scratchpad	O
RAM	B-Architecture
and	O
a	O
12-bit	O
address	B-General_Concept
space	I-General_Concept
,	O
allowing	O
it	O
to	O
be	O
packaged	O
in	O
a	O
28-pin	O
dual	B-Algorithm
in-line	I-Algorithm
package	I-Algorithm
(	O
DIP	B-Algorithm
)	O
,	O
compared	O
to	O
the	O
40-pin	O
packaging	O
of	O
most	O
designs	O
of	O
the	O
era	O
like	O
the	O
Zilog	B-General_Concept
Z80	I-General_Concept
or	O
MOS	B-General_Concept
6502	I-General_Concept
.	O
</s>
<s>
It	O
also	O
included	O
a	O
separate	O
seven-level	O
call	B-General_Concept
stack	I-General_Concept
of	O
12-bit	O
addresses	O
so	O
subroutine	O
calls	O
did	O
not	O
have	O
to	O
use	O
the	O
scratchpad	O
.	O
</s>
<s>
This	O
allowed	O
a	O
simple	O
controller	O
to	O
be	O
implemented	O
in	O
two	O
chips	O
,	O
the	O
9002	O
and	O
a	O
ROM	B-Device
,	O
along	O
with	O
any	O
required	O
interface	O
hardware	O
like	O
an	O
Intel	O
8212	O
or	O
even	O
just	O
a	O
flip-flop	B-General_Concept
.	O
</s>
<s>
Unfortunately	O
for	O
Electronic	O
Arrays	O
,	O
ramping	O
up	O
the	O
depletion-load	O
fabrication	O
line	O
did	O
not	O
go	O
as	O
well	O
as	O
it	O
did	O
for	O
companies	O
like	O
MOS	B-Architecture
Technology	I-Architecture
,	O
and	O
by	O
the	O
end	O
of	O
1976	O
they	O
were	O
still	O
struggling	O
with	O
yields	O
.	O
</s>
<s>
By	O
the	O
next	O
year	O
,	O
chips	O
like	O
the	O
6502	B-General_Concept
and	O
Z80	B-General_Concept
were	O
hitting	O
their	O
production	O
stride	O
and	O
the	O
EA9002	B-General_Concept
still	O
had	O
no	O
significant	O
design	O
wins	O
.	O
</s>
<s>
One	O
electronics	O
company	O
,	O
the	O
Pro-Log	O
Corporation	O
of	O
Monterey	O
,	O
California	O
,	O
used	O
the	O
9002	O
in	O
a	O
single-board	B-Device
computer	I-Device
in	O
early	O
1977	O
.	O
</s>
<s>
In	O
the	O
first	O
edition	O
of	O
An	O
Introduction	O
to	O
Microcomputers	B-Architecture
,	O
Adam	O
Osborne	O
devoted	O
a	O
chapter	O
to	O
the	O
9002	O
.	O
</s>
<s>
He	O
described	O
it	O
as	O
a	O
combination	O
of	O
the	O
Fairchild	B-General_Concept
F8	I-General_Concept
and	O
RCA	B-General_Concept
COSMAC	I-General_Concept
,	O
in	O
that	O
it	O
had	O
the	O
scratchpad	O
memory	O
and	O
overall	O
concept	O
of	O
the	O
F8	O
with	O
the	O
multiple	O
general	O
purpose	O
registers	O
of	O
the	O
COSMAC	O
.	O
</s>
<s>
However	O
,	O
by	O
the	O
time	O
the	O
second	O
edition	O
was	O
published	O
in	O
1977	O
,	O
the	O
chapters	O
covering	O
the	O
EA9002	B-General_Concept
and	O
Rockwell	O
PPS-8	O
were	O
removed	O
as	O
the	O
former	O
had	O
been	O
cancelled	O
and	O
the	O
latter	O
never	O
released	O
.	O
</s>
<s>
The	O
9002	O
had	O
55	O
instructions	O
,	O
patterned	O
on	O
the	O
Intel	B-General_Concept
4040	I-General_Concept
.	O
</s>
<s>
Separate	O
instructions	O
were	O
also	O
needed	O
to	O
read	O
and	O
write	O
the	O
internal	O
scratch	O
RAM	B-Architecture
,	O
which	O
otherwise	O
operated	O
like	O
external	O
memory	O
and	O
had	O
to	O
be	O
loaded	O
and	O
saved	O
through	O
the	O
accumulator	O
using	O
and	O
.	O
</s>
<s>
The	O
arithmetic	B-General_Concept
logic	I-General_Concept
unit	I-General_Concept
(	O
ALU	O
)	O
supported	O
both	O
binary	O
and	O
packed	O
binary	O
coded	O
decimal	O
(	O
BCD	O
)	O
arithmetic	O
,	O
as	O
was	O
common	O
for	O
the	O
era	O
.	O
</s>
<s>
EA	O
did	O
have	O
a	O
line	O
of	O
ROMs	O
and	O
static	B-Architecture
RAM	I-Architecture
,	O
and	O
around	O
the	O
same	O
time	O
they	O
introduced	O
a	O
new	O
32x1	O
(	O
4	O
kB	O
)	O
ROM	B-Device
which	O
was	O
often	O
illustrated	O
being	O
used	O
with	O
the	O
9002	O
.	O
</s>
<s>
Development	O
was	O
carried	O
out	O
with	O
a	O
macro	B-Language
assembler	I-Language
running	O
on	O
the	O
IBM	B-Application
System/360	I-Application
which	O
was	O
also	O
available	O
online	O
with	O
National	O
CSS	O
.	O
</s>
<s>
ASM/GEN	O
and	O
SIM/GEN	O
,	O
systems	O
for	O
developing	O
for	O
cross-assemblers	O
and	O
simulators	O
in	O
FORTRAN	O
IV	O
,	O
supported	O
the	O
EA9002	B-General_Concept
as	O
a	O
target	O
.	O
</s>
