Appendix
B-2230
Operators
INTERCONNECTION RULES
There
are
several simple
rules
that satisfy most
RS-232-C interconnections requirements.
1.
A standard RS-232-C cable connects a
DTE
device
to a
DCE
device. Both devices must adhere to the electri-
cal
and
mechanical specifications of the RS-232-C stan-
dard.
The
standard cable has a female connector
on
one
end
and
a
male
connector
on
the other
end.
The
Transmit
and
Receive conductors
are
not interchanged.
The
stan-
dard RS-232-C cable
is
sometimes referred to
as
a
"straight through" cable.
In
Table B-1, the Cable-Type
Identification table, the straight-through cable
is
referred to
as
Type A.
2.
A "Null Modem" cable or device may
be
used
to
interconnect two
DTE
or two
DCE
devices. Generally the
cable
is
custom
made
with RS-232-C connectors that
match the devices to
be
interconnected. A
null
modem
cable permits two devices of the
same
type
(DCE
to
DCE
and
DTE
to
DTE)
to communicate
as
if they were con-
nected
DTE
to
DCE.
The
Transmit
and
Receive
lines
and
the associated handshake
line
are
swapped
in
the
null
modem to satisfy the requirements for data transfer
between the two devices.
See
Figure
B-1
for the "Null
Modem" cable wiring schematic.
RS-232-C
DTE
DEVICE
1
PIN
1
2
3
4
5
6
7
8
20
3. A "Gender Changer" has straight-through connec-
tions that may
be
used
to convert a non-standard port
connector
(a
DTE
device with a female connector or a
DCE
device with a
male
connector) for connection with a
standard RS-232-C cable. Gender changers come as
male-to-male
and
female-to-female.
The
male-to-male
changer
is
the most
used.
The
gender changer
is
connected between the non-
conforming device
and
the appropriate
end
of a standard
RS-232-C cable. Situations
may
occur when neither device
has conforming connectors;
in
that
case,
use gender
changers
on
both devices to permit interconnection with a
standard RS-232-C cable (or use
one
of the specified
cables from Table
B-1).
4.
If non-standard cabling or connectors
are
used,
an
interconnection terminal box
may
be
needed
to provide
user-customized hookups.
The
2200
Family
DSOs
have
both a
DTE
port
and
a
DCE
port to
make
it easy to connect to either a
DTE
or a
DCE
device using a standard RS-232-C cable. Both con-
nectors conform to the electrical
and
mechanical
specifications of the RS-232-C. Therefore,
in
most cases,
you
should not have to modify the 2200 Family
DSO
end
of
an
interconnection cable to hook
up
other devices with
the oscilloscope.
RS-232-C
DTE
DEVICE
2
PIN
1
2
3
4
5
6
7
8
20
6530-18
Figure B-1. Null Modem cable wiring (non-handshaking).
8-2
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