The Modbus/TCP
Serial Boxed Converter enables serial devices communicating on RS232/485 using the
Modbus protocol, such as MOD-MUX modules, to be connected to an Ethernet
network.
The Modbus/TCP
Converter performs two functions. The first being a modbus converter from
Ethernet to RS232/485, and the second being a Web Server for configuration and
diagnostic purposes.
The converter
communicates using the standard Modbus/TCP protocol. This protocol is supported
by many of the SCADA packages which are on the market. The result is a very
simple and efficient way of connecting MOD-MUX devices to a PC or PLC on an
Ethernet network. The converter supports 4 TCP sockets. This means that up to 4
devices can communicate with the MOD-MUX modules via the converter at any one
time.
An added
advantage of using the converter, is that the Modbus RS485 network can be split
into a number of smaller networks, each with a separate converter. This
increases throughput dramatically as the single Ethernet network has a much
higher bandwidth than the individual RS485 networks and overall data polling
times are reduced accordingly.
Each
Modbus/TCP Converter has a unique Ethernet IP address which must be programmed
into the PC or PLC. The IP address in the converter is configured via the Web
Server. Any standard Web browser such as Internet Explorer can be used to access
the web pages were configuration is carried out. The converters are factory
programmed with a default IP address of 169.254.111.111. This address must be
changed before the converter is added to an existing network.
The web page
address for viewing the setup parameters is http://169.254.111.111/index.htm
The web page address for configuring the converter is http://169.254.111.111/ip.htm
The
master device which is polling the modules must be configured with the IP
address of the converter and with the modbus ID of the MOD-MUX modules. As each
RS485 network is separate, it is possible to have repeated MOD-MUX ID's on the
RS485 networks. The IP address differentiates between the different RS485
networks. Consequently, many hundreds of MOD-MUX modules may be added to a
Ethernet network.
 | SPECIFICATIONS |
Power Supply: 10 - 26 Vdc @ 140 mA
Ethernet:
10BaseT - 10Mbits/s twisted pair
RS485:
2 Wire Multidrop twisted pair -
Internal Jumper
RS232:
3 Wire , TX,RX,GND
Baud
Rate:
2400, 4800, 9600 and 19200.
Data Bits:
5, 6, 7, 8 .
Parity:
none, even, odd.
Stop Bits:
1, 2.
Connector: 8
Way screw terminals on removable plug.
RJ45 on front of module for 10Base-T Ethernet
Power must be applied to terminal
8 (+12/24VDC) and terminal 7 (0V). The power LED will illuminate and all LED's will
be off.
Next the
Ethernet connection is required, either through a network or directly to a PC.
The Ethernet interface uses a standard RJ45 connector.
If the PC is
equipped with an Ethernet card but not connected to a network, a local network
address should be used for communication between the Converter and the PC. The
Converter is shipped with a default IP address 169.254.111.111. This address is
in the address area reserved for local networks not connected to the Internet.
For direct connection between the PC and the converter, a crossover Ethernet
cable is required.
To setup your
PC to connect directly to the Converter, an IP address in the same range as the
Converter must be assigned to the PC. In Windows environments, this should be
done as follows:
·
Connect the PC and the Converter together using
a crossover cable
·
Open the Windows Control Panel
·
Select Network
·
Select TCP/IP -> the PC's Ethernet adaptor
from the Configuration tab as shown below
| Click
the properties button. A TCP/IP Properties box similar to the one below
should appear |
| Select
the IP Address tab |
| Choose
to Specify an IP address as shown in the figure |
| Insert
the IP address 169.254.111.112 and the corresponding subnet mask as shown |
| Save
your settings by pressing OK in both TCP/IP properties and Network
properties |
| Reboot
your PC |
If there is an Ethernet network
available, the Converter can be connected to any Ethernet connection or hub
belonging to the network. If the PC is connected to a network, there is a strong
possibility that the default IP address of the Converter is outside the range of
the network (the address doesn't belong to the IP subset of the network). If the
Ethernet network is connected to the Internet, this is certain. In this case a
new IP address for the Converter is required. Contact the local network
administrator to be assigned a free IP address for the Converter. The new IP
address is programmed into the Converter using a Web browser software such as
Internet explorer. In this case the Converter must first be connected directly
to a PC as described above.
In the remainder of this chapter,
the IP address 169.254.111.111 is used as an example. Exchange this IP address
with the IP address you have set up in all the occurrences.
To test the connection between the PC
and the Converter, a simple program called ping can be used. Ping
sends a number of messages to the specified IP address and displays the
response. The ping program can be run from the command line or from a DOS window
on the PC, as follows:
| Open the Windows Start Menu |
| Click
Run |
| In
the Open box, type: "ping 169.254.111.111" |
If the network connection is OK,
the program will respond with:
"Reply from 169.254.111.111" and information about the response time.
If there is a problem with the
network setup the program will respond:
"Destination host unreachable". There may be two solutions to
this problem:
| If
the PC is connected in a network, change the IP address to an address
accessible from the local network. |
| If
the Converter is connected directly to the PC(or through a hub), change the
PC's IP address to one in the same address range as the Converter. |
If there is a problem with the
Converter the program will respond:
"Request timed out", this means that the Converter can not
respond to messages. Check the power connection. Check that the Link LED is
illuminated when the cable is plugged into the RJ45 connector.
The Converter has two built in web
pages. The first being for checking the configuration and the second is for
altering the configuration. To view these Web pages, a Web browser such as
Internet Explorer or Netscape is needed.
When using the Converter there is
no DNS (Domain Name Server) to recognize the IP address and assign a symbolic
name for it (for instance www.proconel.com). To use
symbolic names, contact the local network administrator and ask for a symbolic
name for a specified IP address.
To view the default Web page in
the Converter, start the Web browser and type "169.254.111.111" into
the address line of the browser window. The main page of the Converter will now
be displayed in the browser window.
To view the
default Web page in the Converter, start the Web browser and type
"169.254.111.111" into the address line of the browser window. The
main page of the Converter will now be displayed in the browser window.
If no Web page is displayed, go back to
testing the network connection to the Converter by using the ping command. If
the Converter replies to the ping messages, check the setup of the Web browser.
If the Converter is directly connected to the same network as the PC,
"direct connection to the network" or "bypass proxy server for
local addresses" should be selected in the Web browser configuration menu.
If the Converter is connected to the PC through a firewall, a proxy server
should be selected in the configuration menu. Contact the local network
administrator for information about the network configuration.
The Web page
address "169.254.111.111/ip.htm" is entered into the address line of
the browser window to access the configuration page. This page allows you to
change the IP address of the MOD-MUX TCP Module, select serial timeout, to setup
the baud rate of the MOD-MUX TCP Module on the RS485 network, and to enter a
Module Description Name for identification/maintenance purposes.
| IP
Address: The new IP
address can be entered into the web page as shown above. After this has been
done, you must click the Submit button to send the values to the MOD-MUX TCP
Module. The screen will now be updated and if successful will continue to
display the new IP address. The new IP address will only be effective after
the MOD-MUX TCP Module power has been switched off and on again. This
feature allows you to check that the correct IP address has been entered
before being activated. If the IP address has been entered incorrectly and
the power has not been switched off, it is possible to re-enter the correct
IP address. If the power has been switched off and back on again, the
MOD-MUX TCP Module will not communicate until you enter the new IP address
into the address line of the browser window.
|
| Baud Rate, Data Bits,
Parity, Stop Bits:
The configuration of the serial port can be configured by selecting the
parameters from the pull-down menu. Click on the Submit button to load these
values into the MOD-MUX TCP Module.
|
| Serial
Timeout: This
timeout is the time the module waits for a reply from a slave device. If a
reply is received then this timeout is cancelled and the converter looks for
the next TCP message. If the slave does not send a reply, then this timeout
will expire and allow the converter to look for the next TCP message. This
timeout must be longer than the turn-around time of the slave device or it
will timeout before the slave replies.
|
| Serial Tx On Time:
This is the time the RS485 transmitter will be enabled before data is
transmitted. This has no effect on RS232 communications.
|
| Serial Tx Off Time:
This is the time the RS485 transmitter will be enabled after data is
transmitted. This has no effect on RS232 communications.
|
| Module
Name: This field
allows you to enter a module description name into the MOD-MUX TCP Module.
This is an identifier for diagnostic/maintenance purposes and is chosen to
best describe the MOD-MUX TCP Module in the system by name or number. |
|
No
|
Checkpoint
|
|
Solution
|
|
|
|
|
|
|
1
|
Is
the LINK LED on and is the ACTIVITY LED flashing with short pulses?
|
No
|
No network connection is
detected. The Ethernet cable is either not plugged in or wrong type of
cable is used. For connection to a network with a hub or switch, a
normal network cable can be used. For direct connection to a PC network
card, a twisted cable must be used.
|
|
Yes
|
A network connection is
detected, the Converter is connected to the network.
|
|
2
|
Does
the Converter respond to PING requests?
|
No
|
Either the PC or the Converter
is setup with wrong IP address.
To change the IP address of the
Converter back to the default address, open the Converter housing and
remove the jumper labeled SIP2. Apply power to the Converter for a short
while. Now replace the jumper and close the enclosure.
To change the IP address of a
PC, use the Windows "control panel -> network -> TCP/IP
properties" and setup an IP address close to the Converter address.
The Converter is shipped with a default IP address of 169.254.111.111,
the PC can be setup with an IP address of 169.254.111.112
|
|
Yes
|
The PC and Converter are setup
with a correct IP address and they are able to communicate with each
other.
|
|
3
|
Can
the default Web page be accessed in a Web browser?
|
No
|
This is normally caused by the
setup of the Web browser.
In the "options" or
"preferences" menu, check that the Web browser is configured
for direct network connection or local area network and NOT using
a proxy server.
|
|
Yes
|
No problems.
|
| 
