<s>
National	O
Semiconductor	O
's	O
INS8060	B-Device
,	O
or	O
SC/MP	O
(	O
pronounced	O
scamp	O
)	O
for	O
Simple	O
Cost-effective	O
Micro	B-Architecture
Processor	I-Architecture
,	O
is	O
an	O
early	O
8-bit	O
microprocessor	B-Architecture
which	O
became	O
available	O
in	O
April	O
1976	O
.	O
</s>
<s>
A	O
unique	O
feature	O
of	O
the	O
SC/MP	O
is	O
a	O
daisy-chained	O
control	O
pin	O
that	O
allowed	O
up	O
to	O
three	O
SC/MP	O
'	O
s	O
share	O
a	O
single	O
main	O
memory	O
to	O
produce	O
a	O
multiprocessor	B-Operating_System
system	O
.	O
</s>
<s>
To	O
lower	O
cost	O
,	O
the	O
system	O
used	O
a	O
bit-serial	O
arithmetic	B-General_Concept
logic	I-General_Concept
unit	I-General_Concept
(	O
ALU	O
)	O
and	O
was	O
thus	O
significantly	O
slower	O
than	O
contemporary	O
designs	O
like	O
the	O
Intel	B-General_Concept
8080	I-General_Concept
or	O
MOS	B-General_Concept
6502	I-General_Concept
which	O
had	O
parallel	O
ALUs	O
.	O
</s>
<s>
Another	O
oddity	O
was	O
that	O
the	O
program	B-General_Concept
counter	I-General_Concept
could	O
only	O
access	O
the	O
lower	O
12-bits	O
of	O
the	O
16-bit	B-Device
address	O
,	O
and	O
the	O
upper	O
4-bits	O
had	O
to	O
be	O
set	O
using	O
special	O
instructions	O
.	O
</s>
<s>
The	O
combination	O
of	O
slow	O
speed	O
and	O
paged	O
memory	O
limited	O
its	O
attractiveness	O
,	O
especially	O
in	O
the	O
markets	O
that	O
might	O
need	O
a	O
multiprocessing	B-Operating_System
system	O
.	O
</s>
<s>
Like	O
most	O
8-bit	O
microprocessors	B-Architecture
of	O
the	O
era	O
,	O
the	O
SC/MP	O
is	O
based	O
around	O
a	O
16-bit	B-Device
address	O
and	O
an	O
8-bit	O
data	B-General_Concept
bus	I-General_Concept
.	O
</s>
<s>
To	O
lower	O
pin	O
count	O
,	O
the	O
external	O
address	O
bus	O
contains	O
only	O
12	O
pins	O
,	O
sharing	O
4	O
pins	O
from	O
the	O
data	B-General_Concept
bus	I-General_Concept
to	O
create	O
a	O
complete	O
16-bit	B-Device
address	O
.	O
</s>
<s>
Internally	O
,	O
the	O
program	B-General_Concept
counter	I-General_Concept
is	O
twelve	O
bits	O
wide	O
,	O
and	O
there	O
are	O
separate	O
instructions	O
to	O
set	O
the	O
upper	O
four	O
bits	O
.	O
</s>
<s>
Internally	O
it	O
provided	O
five	O
registers	O
plus	O
the	O
program	B-General_Concept
counter	I-General_Concept
.	O
</s>
<s>
Subroutine	O
and	O
Interrupt	O
handling	O
were	O
implemented	O
by	O
Pointer	O
Register	O
3	O
(	O
P3	O
)	O
although	O
this	O
could	O
also	O
be	O
used	O
as	O
a	O
general	O
purpose	O
16	B-Device
bit	I-Device
Index	O
register	O
.	O
</s>
<s>
A	O
unique	O
feature	O
of	O
the	O
SC/MP	O
was	O
a	O
shared	O
daisy-chained	O
control	O
line	O
that	O
allowed	O
multiple	O
SC/MP	O
,	O
or	O
more	O
commonly	O
a	O
single	O
SC/MP	O
and	O
related	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
controllers	O
,	O
to	O
share	O
access	O
to	O
a	O
single	O
main	O
memory	O
.	O
</s>
<s>
The	O
original	O
idea	O
was	O
to	O
ease	O
the	O
creation	O
of	O
microcontroller-like	O
applications	O
containing	O
an	O
SC/MP	O
,	O
one	O
or	O
more	O
DMA	B-General_Concept
controllers	I-General_Concept
,	O
and	O
a	O
single	O
shared	O
memory	O
.	O
</s>
<s>
SC/MP	O
increments	O
the	O
program	B-General_Concept
counter	I-General_Concept
before	O
fetching	O
the	O
instruction	O
,	O
so	O
that	O
on	O
reset	O
it	O
actually	O
starts	O
executing	O
instructions	O
from	O
location	O
0001	O
.	O
</s>
<s>
This	O
also	O
needs	O
to	O
be	O
taken	O
into	O
account	O
for	O
calculating	O
displacements	O
,	O
since	O
the	O
offset	O
will	O
be	O
added	O
to	O
the	O
program	B-General_Concept
counter	I-General_Concept
which	O
will	O
be	O
still	O
pointing	O
to	O
the	O
location	O
of	O
the	O
displacement	O
and	O
not	O
the	O
next	B-General_Concept
instruction	I-General_Concept
.	O
</s>
<s>
The	O
SC/MP	O
was	O
also	O
used	O
as	O
the	O
basis	O
of	O
a	O
single	O
board	O
microcontroller	B-Architecture
produced	O
by	O
Science	O
of	O
Cambridge	O
(	O
later	O
Sinclair	O
Research	O
Ltd	O
)	O
called	O
the	O
MK14	B-Device
.	O
</s>
<s>
Montgomery	O
Elevator	O
Co	O
of	O
Moline	O
IL	O
(	O
later	O
purchased	O
by	O
KONE	O
,	O
Inc	O
)	O
used	O
the	O
SC/MP	O
as	O
the	O
basis	O
for	O
its	O
first	O
micro	B-Architecture
processor	I-Architecture
based	O
elevator	O
controller	O
released	O
in	O
1975	O
.	O
</s>
