Theory of Operation 17
2 • Theory of Operation
This
chapter
provides
information
for
local
device
connections,
the
bridge
to
the
host
PCI,
and
the
general
system
ʹ
s
function.
The
design
of
the
PMC423
is
illustrated
in
the
block
diagram
that
follows.
2.1 PMC423 Block Diagram
Figure 2-1 PMC423 Block Diagram
The
PMC423
can
operate
with
the
32
‐
bit
33/66MHz
PCI
bus,
+3.3V
or
+5V
PCI
signaling.
This
allows
for
the
maximum
flexibility
for
the
different
PCI
bus
speeds,
and
signaling.
The
signaling
level
for
the
serial
communication
(RS232,
RS422,
etc.)
are
configured
via
the
software.
The
card
generates
the
necessary
voltage
for
the
serial
signaling
onboard
using
the
+5V
supply.
This
allows
the
PMC423
to
operate
from
the
+3.3V
and
+5V
supply
only.
There
are
two
eight
port
serial
devices
that
are
after
the
PCI
to
PCI
bridge
for
a
total
of
sixteen
ports.
Due
to
the
density
of
the
serial
ports,
the
hardware
handshake
signals
have
not
been
routed
to
the
front
or
the
rear
of
the
card.
PCI/PCI Bridge
Host PCI
8 Port Serial
L
L
L
o
o
o
c
c
c
a
a
a
l
ll
P
P
P
C
C
C
I
II
B
B
B
u
u
u
s
s
s
Signal
Conditioning
8 Port Serial
Signal
Conditioning
Signal
Conditioning
Signal
Conditioning
1
Port
2
3 4 5
6
16
15
14
13
7
8 9
10
11
12
Port
