<s>
A	O
power-on	B-Application
reset	I-Application
(	O
PoR	O
,	O
POR	O
)	O
generator	O
is	O
a	O
microcontroller	B-Architecture
or	O
microprocessor	B-Architecture
peripheral	O
that	O
generates	O
a	O
reset	B-General_Concept
signal	O
when	O
power	O
is	O
applied	O
to	O
the	O
device	B-Architecture
.	O
</s>
<s>
It	O
ensures	O
that	O
the	O
device	B-Architecture
starts	O
operating	O
in	O
a	O
known	O
state	B-Application
.	O
</s>
<s>
In	O
VLSI	O
devices	O
,	O
the	O
power-on	B-Application
reset	I-Application
(	O
PoR	O
)	O
is	O
an	O
electronic	O
device	B-Architecture
incorporated	O
into	O
the	O
integrated	O
circuit	O
that	O
detects	O
the	O
power	O
applied	O
to	O
the	O
chip	O
and	O
generates	O
a	O
reset	B-General_Concept
impulse	O
that	O
goes	O
to	O
the	O
entire	O
circuit	O
placing	O
it	O
into	O
a	O
known	O
state	B-Application
.	O
</s>
<s>
A	O
simple	O
PoR	O
uses	O
the	O
charging	O
of	O
a	O
capacitor	O
,	O
in	O
series	O
with	O
a	O
resistor	O
,	O
to	O
measure	O
a	O
time	O
period	O
during	O
which	O
the	O
rest	O
of	O
the	O
circuit	O
is	O
held	O
in	O
a	O
reset	B-General_Concept
state	B-Application
.	O
</s>
<s>
A	O
Schmitt	O
trigger	O
may	O
be	O
used	O
to	O
deassert	O
the	O
reset	B-General_Concept
signal	O
cleanly	O
,	O
once	O
the	O
rising	O
voltage	O
of	O
the	O
RC	B-Algorithm
network	I-Algorithm
passes	O
the	O
threshold	O
voltage	O
of	O
the	O
Schmitt	O
trigger	O
.	O
</s>
<s>
The	O
resistor	O
and	O
capacitor	O
values	O
should	O
be	O
determined	O
so	O
that	O
the	O
charging	O
of	O
the	O
RC	B-Algorithm
network	I-Algorithm
takes	O
long	O
enough	O
that	O
the	O
supply	O
voltage	O
will	O
have	O
stabilised	O
by	O
the	O
time	O
the	O
threshold	O
is	O
reached	O
.	O
</s>
<s>
One	O
of	O
the	O
issues	O
with	O
using	O
RC	B-Algorithm
network	I-Algorithm
to	O
generate	O
PoR	O
pulse	O
is	O
the	O
sensitivity	O
of	O
the	O
R	O
and	O
C	O
values	O
to	O
the	O
power-supply	O
ramp	O
characteristics	O
.	O
</s>
<s>
When	O
the	O
power	O
supply	O
ramp	O
is	O
rapid	O
,	O
the	O
R	O
and	O
C	O
values	O
can	O
be	O
calculated	O
so	O
that	O
the	O
time	O
to	O
reach	O
the	O
switching	O
threshold	O
of	O
the	O
schmitt	O
trigger	O
is	O
enough	O
to	O
apply	O
a	O
long	O
enough	O
reset	B-General_Concept
pulse	O
.	O
</s>
<s>
When	O
the	O
power	O
supply	O
ramp	O
itself	O
is	O
slow	O
,	O
the	O
RC	B-Algorithm
network	I-Algorithm
tends	O
to	O
get	O
charged	O
up	O
along	O
with	O
the	O
power-supply	O
ramp	O
up	O
.	O
</s>
<s>
So	O
when	O
the	O
input	O
schmitt	O
stage	O
is	O
all	O
powered	O
up	O
and	O
ready	O
,	O
the	O
input	O
voltage	O
from	O
the	O
RC	B-Algorithm
network	I-Algorithm
would	O
already	O
have	O
crossed	O
the	O
schmitt	O
trigger	O
point	O
.	O
</s>
<s>
This	O
means	O
that	O
there	O
might	O
not	O
be	O
a	O
reset	B-General_Concept
pulse	O
supplied	O
to	O
the	O
core	O
of	O
the	O
VLSI	O
.	O
</s>
<s>
On	O
an	O
IBM	O
mainframe	O
,	O
a	O
power-on	B-Application
reset	I-Application
(	O
POR	O
)	O
is	O
a	O
sequence	O
of	O
actions	O
that	O
the	O
processor	O
performs	O
either	O
due	O
to	O
a	O
POR	O
request	O
from	O
the	O
operator	O
or	O
as	O
part	O
of	O
turning	O
on	O
power	O
.	O
</s>
<s>
The	O
operator	O
requests	O
a	O
POR	O
for	O
configuration	O
changes	O
that	O
cannot	O
be	O
recognized	O
by	O
a	O
simple	O
System	O
Reset	B-General_Concept
.	O
</s>
