Appendix C. Matching
SDM-SIO1A connections to an
SDM-SIO1
This
section
is
provided
for
users
who
are
familiar
with
the
older
SDM-SIO1,
so
they
can
cross
reference
connections
between
the
new
and
old
devices.
The
SDM-SIO1A
has
fewer
terminals
and
different
labe
l
ling
than
the
SDM-SIO1.
It
does,
however,
perform
in
exactly
the
same
way
and
can
be
used
as
a
drop-in
substitute
with
only
minor
changes
to
the
wiring.
It
has
fewer
terminals
because
the
Z,
Y,
B,
and
A
terminals
are
not
present.
For
the
SDM-SIO1
these
terminals
were
connected
internally
to
the
Tx,
RTS,
CTS
and
Rx
terminals
respectively
and
were,
therefore,
duplicates.
RS-422
and
RS-485
devices
can
be
connected
to
the
equivalent
multifunction
terminals
on
the
SDM-SIO1A.
The
labe
l
ling
for
the
RS-422/RS-485
functions
has
also
been
changed
to
avoid
the
confusion
caused
by
different
lab
el
ling
conventions
used
for
the
A
and
B
terminals
by
different
manufacturers.
To
avoid
this,
the
SDM-SIO1A
uses
the
alternative
TD–,
TD+,
RD–,
RD+
scheme
of
labe
l
ling,
with
the
TD–
and
TD+
pair
being
those
used
for
RS-485
half-duplex
connections.
Please
refer
to
for
a
cross
comparison
between
the
connections
for
the
SDM-SIO1
and
the
SDM-SIO1A.
Table C-1: Pin cross connection table for SDM-SIO1 to SDM-SIO1A
SDM-SIO1
SDM-SIO1A
Case text
Pin
Pin
Case text
C1
1
3
C1
C2
2
4
C2
C3
3
5
C3
G
4
2
G
+12V
5
1
+12V
G
6
7
G
RX-A
7
10
Rx/RD+
SDM-SIO1A and SDM-SIO4A Serial Input/Output Modules
39