Technical Note #631

Technical Note #631
Remote Access to a MITSUBISHI PLC using a VT-MODEM
Abstract: This document explains the procedure for dialing and establishing communications with a
MITSUBISHI MELSEC FX-16MT or FX-64MT PLC using a SIXNET industrial modem (VTMODEM-#).
FX-16MT from MITSUBISHI can be controlled remotely via telephone wiring using a SIXNET
industrial modem. The FX-16MT can be programmed to perform its poll of I/O modules or other
devices through the phone connection.
Software Used:
·
·
·
MELSEC MEDOC v2.30
SIXNET VT-MODEM Setup Wizard v1.15
Windows 2000 OS
Hardware Used:
·
·
·
·
·
·
·
(1) PC with a serial port connection to a VT-MODEM-1 via the VT-CABLE-MDM
(1) MITSUBISHI MELSEC FX-16MT PLC (an FX-64MT will also work in this application)
(1) VT-MODEM-2 connected to the MITSUBISHI MELSEC FX-16MT PLC via the VT-CABLE-MDM
cable.
(1) BEI’JERS SC-09 RS232/RS422 converter (DB9 Female RS232 to DB25 Male RS422)
(1) Male-to-Male straight-wired Gender changer (used for the connection between the VT-MODEM-2 and the
BEI’JERS converter cable)
(1) VT-CABLE-MDM (VT-MODEM-1 to PC)
(2) RJ11 telephone cables
Cable Pin-outs:
BEI’JERS SC-09 with gender changer
DB9 Male to PC (DTE)
DB25 Male to 16MT
è
1
8
CD
ç
2
3
RD out
è
3
2
TD out
ç
4
20
DTR
5
5
GND
ç
6
6
DSR
è
7
8
CTS out
ç
8
7
RTS in
All other pins are not connected
VT-CABLE-MDM
DB9 Female to PC (DTE)
1
2
3
4
5
6
7
8
9
ç
ç
è
è
ç
è
ç
ç
DB9 Male to modem (DCE)
1
DCD out
2
RD out
3
TD in
4
DTR in
5
GND
6
DSR out
7
RTS in
8
CTS out
9
RI out
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REV: AUGUST 2000
PC and VT-MODEM-1 Windows Setup:
Note: A SIXNET VT-MODEM-1 was used during testing. However, most internal PC modem cards
will function properly as the dialing modem in this application.
To configure Windows to recognize the VT-MODEM-1, go to Start à Settings à Control Panel à
Phone and Modem options. Next, go to the Modems tab in the Phone and Modem options window, and
then click on Add… Next, check the “Don’t detect my modem; I will select it from list” box and
manually select “Standard 28800 bps Modem” from the modem type list. Refer to screen shots 1 and 2
below for details of how the modems were configured.
Screen Shot 1
Screen Shot 2
Configuring the Software:
· MELSEC MEDOC v2.30 - Using MELSEC MEDOC go to Start à Open and open the project
containing the correct PLC (See Screen Shot 3). Next, go to Transfer à Setup and set the baud rate
for 9600, 7 data bits, Even parity, 2 stop bits (See Screen Shot 4).
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Screen Shot 3
Screen Shot 4
Configuring the Hardware:
VT-MODEM-1 – Connect the VT-MODEM-1 to the PC via the VT-CABLE-MDM. Load the preconfigured 16MT_64MT_vt1.6ms available on the latest SIXNET CD and in the modem section on
www.Get2Support.com by pressing the “Open Configuration File” button located in the “Read
Configuration” window in the VT-MODEM Setup Wizard. Using the SIXNET VT-Modem Setup
Wizard, choose VT-MODEM-1 in the first window. Select the appropriate communications port (in this
case COM 2) with Hardware flow control. Configure the Baud Rate for 9600 with 7 data bits, Even
Parity, and 2 stop bits (See Screen Shot 5).
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Screen Shot 5
In the “Modem Parameters” setup window select “None” in the Flow Control drop down list.
Finally, write the configuration to the modem by clicking on the “Write Configuration to the
Modem” button (See Screen Shots 6 and 7).
Screen Shot 6
·
Screen Shot 7
VT-MODEM-2- Configure the VT-MODEM-2 the same as the VT-MODEM-1, or if available on
your CD or in modem section on www.Get2Support.com, use 16MT_64MT_vt2.6ms. To enable the
Self-Dialing feature in the VT-MODEM-2, check the “Enable Self-Dial” check box in the “SelfDialing Parameters” window in the VT-MODEM setup Wizard and enter the phone number of your
destination modem in the First Number text box (in this case 24). Use of the other features are
optional, but in this case the ID message “VT-MODEM-2” was used to demonstrate the ID message
feature (See Screen Shot 8). Load the configuration to the modem.
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Screen Shot 8
Connecting the Hardware:
· Phone Connections- The two modems were connected to an internal analog phone system through
their Line RJ11 jacks using standard RJ11 telephone cable.
·
Connecting the modems to the devices- Connect the VT-MODEM-1 to the computer’s
communications port 2 via the VT-CABLE-MDM. Connect the VT-MODEM-2 to the DB25 Female
Programming port via the straight-wired male-to-male adapter and the BEI’JERS SC-09
RS232/RS422 adapter cable.
Establishing the connection:
To establish the connection, the Windows program HyperTerminal Should be used. (Note: To perform
this step successfully the MELSEC MEDOC software must be completely closed.) Start
HyperTerminal, and enter a name (In this case the name is FX_16MT). In the “Connect To” window
select the COM port that the VT-MODEM-2 is connected to on your PC (In this case COM 2). In the
“COM 2 Properties” window configure the Baud Rate for 9600 with 7 data bits, Even Parity, and 2 stop
bits (See Screen Shots 9 and 10).
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Screen Shot 9
Screen Shot 10
In HyperTerminal’s main window issue an AT command to verify that the PC and Modem are
communicating. The Modem should send back an “OK”. Then issue an ATDT# command where #
represents the phone number of the VT-MODEM-2 connected to the PLC. When the modems connect
HyperTerminal will display a “Connect 9600” message (See Screen Shot 11). Save the session and
close HyperTerminal completely.
Screen Shot 11
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Open the MELSEC MEDOC project that was previously configured for this application. Go to Transfer
à PLC à Medoc>PLC. When the PC and PLC begin to transfer the program a Transferring status
gauge will appear. When finished a “Transfer Completed” message appears (See Screen Shot 12).
Screen Shot 12
To disconnect the modems close MEDOC completely, and open the saved session of HyperTerminal.
Type “+ + +” (three plus signs) wait for the modem to send an “OK”, type “ATH”, and then press the
Enter button. When the modem sends back an “OK” then the modems have disconnected (See Screen
Shot 13).
Screen Shot 13
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Establishing a connection using the Self-Dialing feature:
To establish remote communication between the PLC and MEDOC software using the Self-Dialing
feature, a dial-up connection must be initiated by the remote VT-MODEM-2. The feature is initiated by
activating a discrete input to the “From PLC” input on the VT-MODEM-2. To verify that the
connection is established and the ID message is sent successfully, use HyperTerminal to monitor the
incoming data at the answering modem. In this case the VT-MODEM-1 was used as the answering
modem. To prepare for the connection, start Windows HyperTerminal (see previous section). To
initiate the Self-Dialing sequence, apply a continuous supply of 10-30 VDC to the “From PLC” input
on the VT-MODEM-2. When the Self-Dialing feature is enabled, the Power LED on the modem
should blink rapidly. You should see the following messages in your HyperTerminal window: Ring,
Connect 9600, and ID String (See Screen Shot 14). To hang-up the connection, disconnect the 10-30
VDC on the “From PLC” input on the modem, and the modem will hang-up automatically.
Screen Shot 14
Conclusion:
This test successfully established communications between a PC and FX-16MT or FX-64MT via
SIXNET industrial modems.
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