<s>
An	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
(	O
IVT	O
)	O
is	O
a	O
data	B-General_Concept
structure	I-General_Concept
that	O
associates	O
a	O
list	O
of	O
interrupt	B-General_Concept
handlers	I-General_Concept
with	O
a	O
list	O
of	O
interrupt	B-General_Concept
requests	I-General_Concept
in	O
a	O
table	O
of	O
interrupt	B-General_Concept
vectors	I-General_Concept
.	O
</s>
<s>
Each	O
entry	O
of	O
the	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
,	O
called	O
an	O
interrupt	B-General_Concept
vector	I-General_Concept
,	O
is	O
the	O
address	O
of	O
an	O
interrupt	B-General_Concept
handler	I-General_Concept
.	O
</s>
<s>
For	O
example	O
,	O
a	O
dispatch	O
table	O
is	O
one	O
method	O
of	O
implementing	O
an	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
.	O
</s>
<s>
Most	O
processors	O
have	O
an	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
,	O
including	O
chips	O
from	O
Intel	O
,	O
AMD	O
,	O
Infineon	O
,	O
Microchip	O
Atmel	B-Architecture
,	O
NXP	O
,	O
ARM	B-Architecture
etc	O
.	O
</s>
<s>
An	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
is	O
used	O
in	O
the	O
three	O
most	O
popular	O
methods	O
of	O
finding	O
the	O
starting	O
address	O
of	O
the	O
interrupt	B-General_Concept
service	I-General_Concept
routine	I-General_Concept
:	O
</s>
<s>
The	O
"	O
predefined	O
"	O
method	O
loads	O
the	O
program	B-General_Concept
counter	I-General_Concept
(	O
PC	O
)	O
directly	O
with	O
the	O
address	O
of	O
some	O
entry	O
inside	O
the	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
.	O
</s>
<s>
While	O
in	O
principle	O
an	O
extremely	O
short	O
interrupt	B-General_Concept
handler	I-General_Concept
could	O
be	O
stored	O
entirely	O
inside	O
the	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
,	O
in	O
practice	O
the	O
code	O
at	O
each	O
entry	O
is	O
a	O
single	O
jump	O
instruction	O
that	O
jumps	O
to	O
the	O
full	O
interrupt	B-General_Concept
service	I-General_Concept
routine	I-General_Concept
(	O
ISR	O
)	O
for	O
that	O
interrupt	B-Application
.	O
</s>
<s>
The	O
Intel	B-General_Concept
8080	I-General_Concept
,	O
Atmel	B-Architecture
AVR	I-Architecture
and	O
all	O
8051	O
and	O
Microchip	O
microcontrollers	O
use	O
the	O
predefined	O
approach	O
.	O
</s>
<s>
The	O
"	O
fetch	O
"	O
method	O
loads	O
the	O
PC	O
indirectly	O
,	O
using	O
the	O
address	O
of	O
some	O
entry	O
inside	O
the	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
to	O
pull	O
an	O
address	O
out	O
of	O
that	O
table	O
,	O
and	O
then	O
loading	O
the	O
PC	O
with	O
that	O
address	O
.	O
</s>
<s>
Each	O
and	O
every	O
entry	O
of	O
the	O
IVT	O
is	O
the	O
address	O
of	O
an	O
interrupt	B-General_Concept
service	I-General_Concept
routine	I-General_Concept
.	O
</s>
<s>
For	O
the	O
"	O
interrupt	B-Application
acknowledge	O
"	O
method	O
,	O
the	O
external	O
device	O
gives	O
the	O
CPU	O
an	O
interrupt	B-General_Concept
handler	I-General_Concept
number	O
.	O
</s>
<s>
The	O
interrupt	B-Application
acknowledge	O
method	O
is	O
used	O
by	O
the	O
Intel	O
Pentium	O
and	O
many	O
older	O
microprocessors	O
.	O
</s>
<s>
When	O
the	O
CPU	O
is	O
affected	O
by	O
an	O
interrupt	B-Application
,	O
it	O
looks	O
up	O
the	O
interrupt	B-General_Concept
handler	I-General_Concept
in	O
the	O
interrupt	B-General_Concept
vector	I-General_Concept
table	I-General_Concept
,	O
and	O
transfers	O
control	O
to	O
it	O
.	O
</s>
