Owner's manual
MSR04X
I
October
200
5
–
Issue 8
9
Triguard
SC300E MSR04XI Serial Communications Module RS232
Figure
2
-
2 Serial
communications
cable
wiring
THEORY OF OPERATION
Triplicated
data
enters
and
leaves
the
module
(Figure
2
-
3 ) via
the
chassis
backplane
connector
J1
and
is
isolated
from
the
MPP
by
bus
transceivers.
Data
for
transmission
is
loaded
into
dual
port
RAM
in
each
of
the
three
circuit
branches
and
is
voted
2
-
oo
-
3 before
being
passed
to
the
USARTs
on
the
daughter
board
where
it
is
serialised
and
sent
to
the
appropriate
communications
port.
Data
received
at
th
e ports
is
converted
to
parallel
form
by
the
USART
and
written
to
dual
port
RAM
in
each
branch,
the
data
is
accompanied
by
information
about
the
status
of
the
ports
and
the
embedded
microprocessor.
The
dual
port
memory
is
then
read
by
the
MPP
via
a second
set
of
transceivers.
The
four
communications
ports
are
configured
to
run
in
full
duplex
mode
using
an
RS232
interface
and
having
a maximum
rate
of
19200
Baud.
The
communications
ports
are
isolated
from
the
module
circuits
by
opto
-
isolators
and
connected
t
o field
connector
J2
at
the
rear
of
the
module.
The
ports
are
capable
of
powering
modems
or
line
drivers
for
transmission
over
long
distances.
Power
for
the
module
circuits
is
derived
from
the
dual
redundant
SC300E
power
supply
units,
individual
auctioneering
and
regulating
circuits
supplying
various
logic
areas.
The
communications
port
opto
-
isolators
and
interfaces
also
have
separate
supplies.