<s>
Embedded	B-Device
System	I-Device
Module	I-Device
,	O
or	O
ESM	O
,	O
is	O
a	O
compact	O
computer-on-module	B-Application
(	O
COM	O
)	O
standard	O
.	O
</s>
<s>
If	O
the	O
ESM	O
module	O
is	O
plugged	O
on	O
a	O
carrier	O
,	O
it	O
relies	O
on	O
the	O
standard	O
PCI	B-Architecture
bus	I-Architecture
as	O
a	O
board-to-board	O
interface	O
.	O
</s>
<s>
The	O
signal	O
assignment	O
of	O
J2	O
is	O
not	O
fixed	O
but	O
can	O
be	O
completely	O
customized	O
,	O
although	O
there	O
are	O
reserved	O
pins	O
for	O
a	O
64-bit	O
PCI	B-Architecture
bus	I-Architecture
interface	O
.	O
</s>
<s>
A	O
large	O
part	O
of	O
the	O
I/O	O
functions	O
on	O
ESMs	O
are	O
often	O
controlled	O
by	O
an	O
onboard	O
FPGA	B-Architecture
component	O
(	O
field-programmable	B-Architecture
gate	I-Architecture
array	I-Architecture
)	O
so	O
that	O
every	O
module	O
can	O
easily	O
be	O
tailored	O
to	O
a	O
specialized	O
application	O
through	O
user-defined	O
functions	O
.	O
</s>
<s>
Such	O
functions	O
are	O
loaded	O
into	O
the	O
FPGA	B-Architecture
as	O
IP	B-Architecture
cores	I-Architecture
.	O
</s>
<s>
Using	O
FPGAs	B-Architecture
also	O
reduces	O
dependence	O
on	O
special	O
controller	O
chips	O
which	O
may	O
become	O
obsolete	O
,	O
thus	O
extending	O
the	O
card	O
's	O
availability	O
.	O
</s>
<s>
ESMs	O
are	O
typically	O
used	O
on	O
boards	O
for	O
CompactPCI	O
and	O
VMEbus	B-Architecture
as	O
well	O
as	O
single-board	B-Device
computers	I-Device
for	O
embedded	O
applications	O
.	O
</s>
<s>
A	O
mechanical	O
specialty	O
of	O
ESM	O
modules	O
is	O
that	O
their	O
connectors	O
are	O
compatible	O
with	O
the	O
PCI-104	B-Device
module	O
standard	O
.	O
</s>
