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3.3
Connecting Directly to a PC
To connect the Isolated Multi-Drop converter directly to a
PC, you need an RS-232 serial cable of not more than 50
feet in length. Make sure the cable is a DCE-DTE cable, not
a null modem cable. The following table lists the minimum
set of required signals and the pin assignments for DB-25 to
DB-25 and DB-9 to DB-25 cable connectors:
Table 3.1 RS-232 Pin Assignments
Pin Number
on Connector
2
3
4
7
8
To connect the converter to a PC, follow these steps while
refering to Figure 3.3 below:
1.
Connect the plug end of an RS-232 serial cable to
the RS-232 port on the Isolated Multi-Drop converter.
2.
Connect the socket end of the serial cable to an
RS-232 port on your computer.
3.
If you are using application software that requires direct
DCD/RTS control, set the DCD/RTS switch to RTS and
the MAN/AUTO switch to MAN. If you are using
application software that does not require the direct
DCD/RTS control, set the MAN/AUTO switch to AUTO,
and use the BAUD thumbwheel to set the data rate to
match that of the application software and the
ACCESS devices on the network. (In automatic mode,
the converter ignores the setting of the DCD/RTS
switch.)
PC
with
Supervisory
Software
Figure 3.2 Connecting the Converter Directly to a PC
Siemens Energy & Automation, Inc.
Signal Name
TxD
RxD
RTS
GND
DCD
RS-232 Cable
50 Ft. Maximum
3
Installing the Converter
4.
Insert the RS-485 connector(s) into the port(s) on the
front of the converter. (Refer to section 3.1 for
instructions on installing a connector on the RS-485
cable.)
5.
Connect the supplied power cord to the 120 VAC
connector on the converter, and plug the other end into
any 120 VAC grounded power source.
6.
Turn the converter's power switch on, and verify that
the
PWR
LED
"Troubleshooting" if the PWR LED is not lit.)
7.
Start your software.
22 AWG Shielded
Twisted-Pair Cable
4000 Ft. Maximum
+
SHLD
Port 4
-
+
SHLD
Port 3
-
+
SHLD
Port 2
-
+
SHLD
Port 1
-
Isolated Multi-Drop
Converter
is
lit.
(Refer
to
Section
+
Device
#1
-
RS-485
Bus
+
Device
# n
-
Up to 32 devices
To Other
RS-485
Devices
5
5
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