<s>
The	O
Texas	B-General_Concept
Instruments	I-General_Concept
SBP0400	I-General_Concept
(	O
SBP	O
=	O
silicon	O
bipolar	O
)	O
,	O
also	O
known	O
as	O
SBC	O
0400	O
and	O
X0400	O
,	O
is	O
a	O
microprogrammable	B-Device
4-bit	O
slice	O
processor	O
that	O
was	O
introduced	O
in	O
1976	O
(	O
delivery	O
began	O
in	O
December	O
1975	O
)	O
.	O
</s>
<s>
It	O
was	O
one	O
of	O
the	O
first	O
LSI	O
processors	O
and	O
was	O
the	O
first	O
device	O
in	O
the	O
USA	O
based	O
on	O
I²L	B-General_Concept
technology	O
(	O
integrated	B-General_Concept
injection	I-General_Concept
logic	I-General_Concept
)	O
.	O
</s>
<s>
The	O
commands	O
are	O
entered	O
bit	O
by	O
bit	O
,	O
whereby	O
the	O
9-bit	O
microinstruction	B-Device
word	O
is	O
divided	O
into	O
four	O
ALU	O
command	O
bits	O
,	O
two	O
target	O
operand	O
and	O
three	O
source	O
operand	O
bits	O
.	O
</s>
<s>
The	O
control	O
switches	O
are	O
:	O
ALUCIN	O
(	O
ripple-carry	O
in	O
)	O
,	O
PCPRI	O
(	O
program	B-General_Concept
counter	I-General_Concept
priority	O
,	O
required	O
to	O
turn	O
on	O
the	O
output	O
LEDs	O
on	O
the	O
address	O
bus	O
,	O
PCCIN	O
(	O
program	B-General_Concept
counter	I-General_Concept
carry-in	O
)	O
,	O
ENCBY2	O
(	O
enable	O
program	B-General_Concept
counter	I-General_Concept
increment	O
by	O
a	O
displacement	O
of	O
1	O
or	O
2	O
)	O
,	O
POS1	O
,	O
POS0	O
(	O
most	O
significant	O
,	O
intermediate	O
,	O
or	O
least	O
significant	O
position	O
of	O
the	O
processor	O
slice	O
in	O
a	O
cascade	O
)	O
.	O
</s>
<s>
Bit	B-General_Concept
slice	I-General_Concept
processor	I-General_Concept
successors	O
from	O
TI	O
were	O
the	O
8-bit	O
SN74AS888	O
and	O
the	O
16-bit	O
SBP9900	O
.	O
</s>
