Vlinx
MESR9xx
Modbus Gateways
Manual Documentation Number MESR9xx-4508m
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Table of Contents
Table of Contents
1.
2.
Introduction.......................................................................................................................................................1
About MESR9xx Modbus Gateways..........................................................................................................................................1
MESR9xx Modbus Gateway Model Numbering.........................................................................................................................2
List of MESR9xx Modbus Gateway Models...............................................................................................................................3
MESR9xx Modbus Gateway Features.......................................................................................................................................4
Vlinx Manager Configuration Software.......................................................................................................................................5
MESR9xx Modbus Gateway Hardware............................................................................................................6
Package Checklist......................................................................................................................................................................6
MESR9xx Modbus Gateway Enclosures and Mounting.............................................................................................................6
LED Indicators............................................................................................................................................................................7
E1/E2 Ethernet Link LED .............................................................................................................................................. 7
Ready LED..................................................................................................................................................................... 7
Serial Port LEDs............................................................................................................................................................ 7
Mode Switch...............................................................................................................................................................................8
Ethernet Connector....................................................................................................................................................................8
Fiberoptic Connectors................................................................................................................................................................9
Serial Port Connectors...............................................................................................................................................................9
Power Connector .....................................................................................................................................................................10
Mounting Hardware..................................................................................................................................................................10
3.
Modbus Gateway Setup and Connections ...................................................................................................12
Connecting the Power Supply..................................................................................................................................................12
Connecting MESR9xx Modbus Gateways to Modbus networks..............................................................................................12
Connecting the MESR901-x ......................................................................................................................................... 13
Connecting the MESR902T-x....................................................................................................................................... 14
Connecting the MESR902D-x ...................................................................................................................................... 14
Connecting MESR9xx Modbus Gateways to a Network..........................................................................................................15
Network Connection (10BaseT/100BaseTX)................................................................................................................ 15
Fiberoptic Connection ................................................................................................................................................. 15
MESR9xx Modbus Gateway Configuration Connections.........................................................................................................15
Configuring the MESR9xx Modbus Gateway via the Network Connection.................................................................. 16
Configuring the MESR9xx Modbus Gateway via the Serial Port (Console Mode) ...................................................... 17
MESR9xx Modbus Gateway Operational Connections............................................................................................................18
Using MESR9xx Modbus Gateways in Direct IP Mode ............................................................................................... 18
Initiating a Hardware Reset on the Modbus Gateway..............................................................................................................19
Reloading Factory Defaults......................................................................................................................................................20
4.
Description, Modbus Gateway Properties....................................................................................................21
Attached...................................................................................................................................................................................21
Baud Rate ................................................................................................................................................................................21
Character Timeout ...................................................................................................................................................................21
Configuration Files ...................................................................................................................................................................21
Data/Parity/Stop.......................................................................................................................................................................22
Default Gateway.......................................................................................................................................................................22
DHCP .......................................................................................................................................................................................22
Firmware Version.....................................................................................................................................................................23
Hardware Version ....................................................................................................................................................................23
ID Routing ................................................................................................................................................................................23
IP Address................................................................................................................................................................................23
Link Status ...............................................................................................................................................................................24
MAC Address...........................................................................................................................................................................24
Modbus Priority ........................................................................................................................................................................24
Modbus Serial Retries..............................................................................................................................................................24
Modbus ASCII..........................................................................................................................................................................25
Modbus Message Buffering .....................................................................................................................................................25
Modbus Message Timeout.......................................................................................................................................................25
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Table of Contents
Modbus RTU Message ............................................................................................................................................................25
Modbus Serial Control..............................................................................................................................................................25
Modbus TCP Message.............................................................................................................................................................26
Model .......................................................................................................................................................................................26
Network Mode..........................................................................................................................................................................26
Network Protocols....................................................................................................................................................................26
Password .................................................................................................................................................................................27
Port# ID Remap .......................................................................................................................................................................27
Serial Interface Modes .............................................................................................................................................................27
Modbus Gateway Name...........................................................................................................................................................28
Gateway Serial Port Number ...................................................................................................................................................28
Subnet Mask ............................................................................................................................................................................28
TCP (Transmission Control Protocol) ......................................................................................................................................29
5.
Upgrading the Modbus Gateway Firmware ..................................................................................................30
Downloading Firmware Files....................................................................................................................................................31
Uploading the Firmware to the Modbus Gateway....................................................................................................................31
6.
7.
Diagnostics .....................................................................................................................................................33
Testing a Modbus Gateway Connection ..................................................................................................................................33
Application Examples.....................................................................................................................................35
From Serial Master to Modbus Gateway, Slave IDs Configurable...........................................................................................35
From Serial Masters To Ethernet Master, Slave IDs Fixed......................................................................................................36
Keep Serial Master, Add Ethernet Master(s) ...........................................................................................................................36
Modbus RTU, ASCII, and TCP Integration ..............................................................................................................................37
8.
9.
Modbus Help ...................................................................................................................................................38
Modbus ASCII/RTU Basics......................................................................................................................................................38
Hints and Tips ..........................................................................................................................................................................39
Appendices .....................................................................................................................................................40
Appendix A: Default Gateway Settings ....................................................................................................................................41
Appendix B: Product Specifications .........................................................................................................................................42
General Specifications ................................................................................................................................................. 43
Controls, Indicators and Connector Specifications...................................................................................................... 44
Serial Interface Specifications ..................................................................................................................................... 45
Network Specifications................................................................................................................................................. 46
Appendix C: Dimensional Diagrams ........................................................................................................................................47
Appendix D: Connector Pinouts...............................................................................................................................................51
MESR901-x Serial Port Pinouts................................................................................................................................... 51
MESR902D-x Serial Port Pinouts................................................................................................................................ 53
MESR902T-x Serial Port Pinouts................................................................................................................................. 54
Standard Ethernet Cable RJ-45 Pin-out....................................................................................................................... 55
10.
Glossary ..........................................................................................................................................................56
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1. Introduction
Vlinx MESR9xx Modbus Gateway
1. Introduction
Thank you for purchasing a MESR9xx Modbus Gateway product! This product has been
manufactured to the highest standards of quality and performance to ensure your
complete satisfaction.
Figure 1. An MESR921 Modbus Gateway
About MESR9xx Modbus Gateways
MESR9xx Modbus Gateways connect Modbus networks (RS-232, RS-422 or RS-485)
to Ethernet networks, allowing the Modbus network to become a node on the network.
The serial ports can be accessed over a LAN/WAN using Direct IP Mode connections.
MESR9xx Modbus Gateways feature 10BaseT or 100BaseTX copper network media and
fiber optic media options, depending on the model. MESR9xx Modbus Gateways are
built for use in industrial environments, featuring an IP30 approved slim line DIN rail
mountable case. They operate from a range of DC power supply voltages and feature
pluggable terminal block power connectors. An external power supply, sold separately, is
required. The photograph above is an MESR921 gateway. The MESR92x units have an
additional Ethernet port which functions much like an Ethernet Switch. MESR90x units
have one Ethernet port.
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1. Introduction
Vlinx MESR9xx Modbus Gateway
MESR9xx Modbus Gateway Model Numbering
MESR9xx Modbus Gateways are a growing family of products. Models are available
with one or two serial connections. Network connection options include
10BaseT/100BaseTX copper or several different fiber optic options. The following
diagram shows the model numbering scheme:
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1. Introduction
Vlinx MESR9xx Modbus Gateway
List of MESR9xx Modbus Gateway Models
The following table lists the various MESR9xx Modbus Gateway models available.
Model Number Features
MESR922T
MESR922T-MT
MESR922T-MC
MESR922T-ST
MESR922T-SC
MESR922T-ST40
MESR922T-SC40
MESR922T-ST80
MESR922T-SC80
MESR921
2 RJ45 Copper, 2 port MEI with TB
1 Multi-mode ST, 1 RJ45 Copper, 2 port MEI with TB
1 Multi-mode SC, 1 RJ45 Copper, 2 port MEI with TB
1 Single-mode ST, 1 RJ45 Copper, 2 port MEI with TB
1 Single-mode SC, 1 RJ45 Copper, 2 port MEI with TB
1 Single-mode 40 Km ST, 1 RJ45 Copper, 2 port MEI with TB
1 Single-mode 40 Km SC, 1 RJ45 Copper, 2 port MEI with TB
1 Single-mode 80 Km ST, 1 RJ45 Copper, 2 port MEI with TB
1 Single-mode 80 Km SC, 1 RJ45 Copper, 2 port MEI with TB
2 RJ45 Copper, 1 port MEI with TB/DB9 Male
MESR921-MT
MESR921-MC
MESR921-ST
1 Multi-mode ST, 1 RJ45 Copper, 1 port MEI with TB/DB9 Male
1 Multi-mode SC, 1 RJ45 Copper, 1 port MEI with TB/DB9 Male
1 Single-mode ST, 1 RJ45 Copper, 1 port MEI with TB/DB9 Male
1 Single-mode SC, 1 RJ45 Copper, 1 port MEI with TB/DB9 Male
1 Single-mode 40 Km ST, 1 RJ45 Copper, 1 port MEI with TB/DB9 Male
1 Single-mode 40 Km SC, 1 RJ45 Copper, 2 port MEI with DB9 Male
1 Single-mode 80 Km ST, 1 RJ45 Copper, 1 port MEI with TB/DB9 Male
1 Single-mode 80 Km SC, 1 RJ45 Copper, 1 port MEI with TB/DB9 Male
MESR921-SC
MESR921-ST40
MESR921-SC40
MESR921-ST80
MESR921-SC80
MESR902T
MESR902T-MT
MESR902T-MC
MESR902T-ST
MESR902T-SC
MESR902T-ST40
1 RJ45 Copper, 2 port MEI with TB
1 Multi-mode ST, 2 port MEI with TB
1 Multi-mode SC, 2 port MEI with TB
1 Single-mode ST, 2 port MEI with TB
1 Single-mode SC, 2 port MEI with TB
1 Single-mode 40 Km ST, 2 port MEI with TB
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1. Introduction
Vlinx MESR9xx Modbus Gateway
Model Number Features
MESR902T-SC40
MESR902T-ST80
MESR902T-SC80
MESR901
1 Single-mode 40 Km SC, 2 port MEI with TB
1 Single-mode 80 Km ST, 2 port MEI with TB
1 Single-mode 80 Km SC, 2 port MEI with TB
1 RJ45 Copper, 1 port MEI with TB/DB9 Male
1 Multi-mode ST, 1 port MEI with TB/DB9 Male
1 Multi-mode SC, 1 port MEI with TB/DB9 Male
1 Single-mode ST, 1 port MEI with TB/DB9 Male
1 Single-mode SC, 1 port MEI with TB/DB9 Male
1 Single-mode 40 Km ST, 1 port MEI with TB/DB9 Male
1 Single-mode 40 Km SC, 2 port MEI with DB9 Male
1 Single-mode 80 Km ST, 1 port MEI with TB/DB9 Male
1 Single-mode 80 Km SC, 1 port MEI with TB/DB9 Male
MESR901-MT
MESR901-MC
MESR901-ST
MESR901-SC
MESR901-ST40
MESR901-SC40
MESR901-ST80
MESR901-SC80
MESR9xx Modbus Gateway Features
• Four series models
•
MESR901-x (single serial port, single Ethernet Port)
•
MESR902T-x (two serial ports with pluggable terminal blocks, single Ethernet
port)
•
•
MESR921-x (single serial port, two Ethernet Ports)
MESR922T-x (two serial ports with pluggable terminal blocks, two Ethernet
Ports)
•
On models with two Ethernet Ports, the second port is an Ethernet pass-
through port. This port functions much like an unmanaged switch.
• Fiber models available for each of the above series
• Multi-interface serial ports
• DB-9M and pluggable terminal block serial port connector options
• All ports are software selectable as RS-232, RS-422 or RS-485 2- and 4-wire
• Configuration can be done via network or direct serial connection
• Slim line DIN rail mountable case
• Accepts DC power over a wide voltage range
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1. Introduction
Vlinx MESR9xx Modbus Gateway
• 10/100 Mbps Ethernet with Auto Selection, Auto MDI/MDIX
• LAN and WAN Communications
• TCP Client or Server operation - configurable
• Firmware Upload for future revisions/upgrades
• Software Support - Windows 2000/2003 Server/XP/Vista x32
• Configuration of Ethernet and serial port settings using Vlinx Manager software
Vlinx Manager Configuration Software
Vlinx Manager configuration software enables you to find connected Modbus gateways,
configure them, upgrade Modbus gateway firmware, and save/load configuration files. It
features a graphical user interface (GUI) that is convenient and easy to use.
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2. Hardware
Vlinx MESR9xx Modbus Gateway
2. MESR9xx Modbus Gateway Hardware
MESR9xx Modbus Gateways are enclosed in DIN rail mountable enclosures and feature
LED indicators, power, Ethernet and serial connectors and a recessed Mode switch.
Package Checklist
MESR9xx Modbus Gateways are shipped with the following items included:
• MESR9xx Modbus Gateway Module
• Quick Start Guide
• CD with User Manual, Quick Start Guide and firmware
MESR9xx Modbus Gateway Enclosures and Mounting
All MESR9xx Modbus Gateway models are built into similar enclosures. Modules are
DIN rail mountable. The MESR92x (shown below) enclosure is larger than the
MESR90x.See the specification table for dimensions.
Figure 2. Front View of an MESR921 Modbus Gateway
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2. Hardware
Vlinx MESR9xx Modbus Gateway
LED Indicators
MESR9xx Modbus Gateways have three types of LED indicators: Ethernet Link LEDs,
a Ready LED and Serial Port LEDs.
Figure 3. Ready Ethernet Port LEDs on 1 and 2 Ethernet Port Modbus Gateways
E1/E2 Ethernet Link LED
The Ethernet Link LED (E1 or E2) illuminates (green) if the Ethernet is connected.
When the LED is blinking it indicates that there is data traffic on the Ethernet link.
E1 is used for all models to connect to the network. E2 is used on MESR92X models, and
is a pass-through Ethernet connector.
Ready LED
The Ready LED (green) blinks if the system is operating correctly, once per second in
normal operating conditions, or three times per second in reset, configuration mode, or
when loading factory defaults. If the LED is off or steady, it indicates the system is not
operating correctly.
Serial Port LEDs
MESR901-x Modbus Gateways feature one serial port. MESR902D, and MESR902T-x
Modbus Gateways feature two serial ports. Each serial port has an associated LED. Serial
Port LEDs blink (green) when data is being transmitted or received on the serial port.
When the LED is On it indicates the serial port is open.
Figure 4. Serial Port LEDs on 1 and 2 Serial Port Modbus Gateways
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2. Hardware
Vlinx MESR9xx Modbus Gateway
Mode Switch
A recessed momentary reset switch is located on the top of the enclosure. To activate the
switch, insert a small plastic tool through the hole in the enclosure and press lightly.
Figure 5. Mode Switch
The Mode switch can be used to:
• Initiate a Hardware Reset
• Enter Console Mode
• Reload factory defaults
Note: Refer to Section 3. Modbus Gateway Setup and Connections for more information on using
the Mode switch.
Ethernet Connector
Modbus gateway models using 10BaseT/100BaseTX network connections use an RJ45
receptacle. The Modbus gateway is connected to a standard Ethernet network drop using
a straight-through RJ45 (male) Ethernet cable.
Figure 6. Ethernet Connectors. E2 is pass-through connection on model shown
Note: Refer to Appendix D for connection pin-outs.
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2. Hardware
Vlinx MESR9xx Modbus Gateway
Fiberoptic Connectors
Modbus gateway models using fiber optic network connections use either SC or ST
connectors, depending on the specific model.
Figure 7. SC and ST Fiberoptic Cable Connectors
Serial Port Connectors
MESR9xx Modbus Gateways use four serial port connector configurations, depending on
the model:
• MESR901-x Modbus Gateways feature one serial port and use a DB-9M
connector for RS-232 and a five-position removeable terminal block for RS-422
and RS-485 connections.
• MESR902T-x Modbus Gateways feature two serial ports, both using five-position
removable terminal blocks for RS-232, RS-422 and RS-485 connections.
• MESR921-x Modbus Gateways feature one serial port and use a DB-9M
connector for RS-232 and a five-position removeable terminal block for RS-422
and RS-485 connections.
• MESR922T-x Modbus Gateways feature two serial ports, both using five-position
removable terminal blocks for RS-232, RS-422 and RS-485 connections.
Figure 8. DB-9 Female Serial Port Connector
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2. Hardware
Vlinx MESR9xx Modbus Gateway
Figure 9. Five-Position Pluggable Terminal Block
Note: Refer to Appendix D for connection pin-outs.
Power Connector
The power connector is a 2-position pluggable terminal block.
Figure 10.
Power Connection
Mounting Hardware
MESR9xx Modbus Gateway modules can be DIN rail mounted. The DIN mounting clip
and spring is included on each module.
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2. Hardware
Vlinx MESR9xx Modbus Gateway
Figure 11.
DIN Clips on Modbus Gateway Modules. Large DIN clips are used on MESR92x, small DIN clips on MESR90x.
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3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
3. Modbus Gateway Setup and Connections
This section describes how to setup and connect MESR9xx Modbus Gateways.
Note: In this section devices to be connected to the Modbus gateway’s serial connection are simply
referred to as the “Modbus network”.
Connecting the Power Supply
Connect a DC power supply to the power terminals on the top of the Modbus gateway.
Polarity of the wires is indicated on the label on the side of the Modbus gateway.
Acceptable voltages are between 10 VDC and 48 VDC. The power supply must be
capable of supplying 4 Watts for MESR90x units or 6 Watts fro MESR92x units.
Figure 12.
MESR Power Connection
Connecting MESR9xx Modbus Gateways to Modbus networks
MESR9xx Modbus Gateways can be configured to connect to Modbus networks using
RS-232, RS-422, RS-485 2-wire and RS-485 4-wire.
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3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
RS-232 connections support eight signal lines plus Signal Ground. Signals are single
ended and referenced to Ground. Default communications parameters are 9600, 8, N, 1
and no flow control implemented.
RS-422 connections support two signal pairs: RXA(-), RXB(+) and TXA(-), TXA(+),
plus GND. The data lines are differential pairs (A & B) in which the B line is positive
relative to the A line in the idle (mark) state. Ground provides a common mode reference.
RS-485 connections support 2-wire or 4-wire operation.
When configured for 4-wire operation the connection supports two signal pairs: RXA(-),
RXB(+) and TXA(-), TXA(+), plus GND. This makes full-duplex operation possible.
The data lines are differential pairs (A & B) in which the B line is positive relative to the
A line in the idle (mark) state. Ground provides a common mode reference.
When configured for 2-wire operation the connection supports one signal pair: DataB(+)
and DataA(-) signal channels using half-duplex operation. The data lines are differential
with the Data B line positive relative to Data A in the idle (mark) state. Ground provides
a common mode reference.
Connecting the MESR9x1-x
The MESR9x1-x has one serial connection that supports RS-232, RS-422 and RS-485
(2- and 4-wire). The unit has two connectors: a DB-9M connector and a 5-position
terminal block.
If you select RS-232 mode when you configure the Modbus gateway, you must connect
the Modbus network to the Modbus gateway via a serial cable. The MESR901 is a DTE.
If the Modbus network is a DTE, use a null modem (cross-over) cable. If the Modbus
network is a DCE, use a straight-through cable.
If you select RS-422 mode, RS-485 2-wire mode, or RS-485 4-wire mode when you
configure the Modbus gateway, you must connect the Modbus network appropriately, via
the 5-position terminal block.
Note: Refer to Appendix D for connector pinout information.
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3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
Figure 13.
MESR901 Connections
Connecting the MESR9x2T-x
The MESR9x2T-x has two serial connections that support RS-232, RS-422 and RS-485
(2- and 4-wire). The unit has two connectors, both of which are 5-position terminal
blocks. Make the appropriate connections to the terminal blocks to match the serial
connection mode you select when configuring the Modbus gateway.
Note: Refer to Appendix D for connector pinout information.
Figure 14.
MESR902T-x Connections
Connecting the MESR9x2D-x
The MESR9x2D-x has two serial connections that support RS-232, RS-422 and RS-485
(2- and 4-wire). The unit has two connectors, both of which are DB-9M connectors. You
must connect the Modbus network to the Modbus gateway via a serial cable. The
MESR902D is a DTE. If the Modbus network is a DTE, use a null modem (cross-over)
cable. If the Modbus network is a DCE, use a straight-through cable.
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3. Setup and Connections
Note: Refer to Appendix D for connector pinout information.
Vlinx MESR9xx Modbus Gateway
Figure 15.
MESR902D-x Connections
Connecting MESR9xx Modbus Gateways to a Network
Network Connection (10BaseT/100BaseTX)
When connecting a Modbus gateway equipped with a 10BaseT/100BaseTX network
connection (RJ45 connector) a standard network cable is connected from the Modbus
gateway to a network drop. PCs configuring and/or communicating with the Modbus
gateway are also connected to the network.
Fiberoptic Connection
When connecting a Modbus gateway equipped with a fiberoptic interface to a
fiberoptic link the appropriate fiberoptic cable must be connected between the Modbus
gateway and the network interface. Refer to Figure 2, “List of MESR9xx Modbus
Gateway Models” at the beginning of this manual for a list of supported fiber types,
distances and connectors.
MESR9xx Modbus Gateway Configuration Connections
MESR9xx Modbus Gateways can be configured over the network or via a serial port.
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3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
Configuring the MESR9xx Modbus Gateway via the Network Connection
When configuring via the network, either Vlinx Manager software or the web interface
can be used.
Configuring with Vlinx Manager
MESR9xx Modbus Gateways can be configured over the network Vlinx Manager
software running on a PC.
To open Vlinx Manager:
1. From the Desktop, click Start Æ Programs Æ B&B Electronics Æ Vlinx Æ Modbus
Gateway Manager Æ Configuration Manager.
The Vlinx Manager Device Discovery window appears.
Figure 16.
Vlinx Manager Discovery Window
2. Configure your Modbus gateway as required.
Note: For more information on configuration options refer to Section 4: Description of Modbus
gateway Properties.
Configuring with the Web Interface
MESR9xx Modbus Gateways can be configured over the network using a standard
internet browser such as Internet Explorer or Firefox.
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3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
To open the web configuration interface:
1. On a PC connected to the network, open a browser.
2. In the browser’s address bar, type the IP address of the Modbus gateway.
Note: Your Modbus gateway comes from the factory pre-configured with the IP address
192.168.0.1, but the Vlinx configuration software will automatically configure the correct address
through DHCP if this is not available.
The web interface Login page appears.
Figure 17.
Vlinx Manager Login Screen
3. Configure your Modbus gateway as required.
Note: For more information on configuration options refer to Section 4: Description of Modbus
Gateway Properties.
Configuring the MESR9xx Modbus Gateway via the Serial Port (Console
Mode)
Your Modbus gateway can be configured via a serial port using Vlinx Manager. To use
this feature the Modbus gateway's serial port must be connected to the serial port of a PC
(using a null modem cable).
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3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
Figure 18.
Console Mode Setup
To configure the Modbus gateway it must be put into Console Mode, using the Mode
switch.
To enter Console Mode, press and hold the Mode switch for between two and ten
seconds. The LED indicators respond as follows:
1. The Ready LED blinks three times per second while the button is being pressed.
2. The Modbus gateway is in Console Mode when:
• On the MESR901: Port 1 LED is On and the Ready LED is Off.
• On MESR902x models: Port 1 LED is On and the Port 2 LED is Off.
To configure the Modbus gateway, open the Vlinx Manager software and set up the
Modbus gateway's parameters as required.
Note: For more information on configuration options refer to Section 4: Description of Modbus
Gateway Properties.
To exit Console Mode, press and hold the Reset switch for two seconds, or turn off the
power from the MESR9xx, wait a few seconds, and turn the power on again.
The LEDs go back to their normal states when the device resumes normal operation.
MESR9xx Modbus Gateway Operational Connections
MESR9xx Modbus Gateways can operate in Direct IP Mode.
Using MESR9xx Modbus Gateways in Direct IP Mode
A Direct IP connection allows applications using TCP/IP socket programs to
communicate with the COM ports on the Modbus gateway. In this type of application the
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3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
Modbus gateway is configured as a TCP server. The socket program running on the PC
establishes a communication connection with the Modbus gateway. The data is sent
directly to and from the serial port on the server.
To set up a Direct IP Mode connection:
1. Connect the Modbus gateway to the network and a Modbus network as described in
previous sections.
2. Configure the Modbus gateway with the appropriate network settings (using Vlinx
Manager or the web interface).
3. Configure your software application with the appropriate IP address and port number
to communicate with the Modbus network(s).
Figure 19.
Direct IP Connection
Initiating a Hardware Reset on the Modbus Gateway
To initiate a Hardware Reset on the Modbus gateway, press and hold the Mode switch
for 0 to 2 seconds, and then release it. The LED indicators respond as follows:
1. The Ready LED blinks three times per second while the button is being pressed.
2. The Modbus gateway is in Reset Mode when:
• On the MESR901: Port 1 LED is On and the Ready LED is Off.
• On MESR902x models: Port 1 LED is On and the Port 2 LED is Off.
3. The LEDs go back to their normal states when the device resumes normal operation.
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3. Setup and Connections
Vlinx MESR9xx Modbus Gateway
Reloading Factory Defaults
To reload Factory Defaults, press and hold the Mode switch for more than 10 seconds.
The LED indicators respond as follows:
1. The Ready LED blinks three times per second while the button is being pressed.
2. The Modbus gateway is in Factory Default Mode when:
• On the MESR901: Port 1 LED and the Ready LED are both On.
• On MESR902x models: Port 1 LED and the Port 2 LED are both On.
The Modbus gateway reloads all factory default configuration parameters.
3. The LEDs go back to their normal states when the device resumes normal operation.
Note: Factor default parameters are listed in Appendix A
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4. Properties
Vlinx MESR9xx Modbus Gateway
4. Description, Modbus Gateway Properties
The following MESR9xx Modbus Gateway properties are ordered alphabetically to assist
you in finding the information you need.
Attached
The Attached is selectable between Master and Slaves. If Master is selected, it will run in
TCP server mode, if Slaves is selected, it will run in TCP client mode.
Baud Rate
Baud Rate is the communication speed of the link between the Modbus gateway and the
device attached to its serial port. Both these devices must be configured to operate at the
same baud rate. Baud rate values range from 75 to 230,400 Baud. (Refer to Appendix B
for specific baud rates that are supported.)
Character Timeout
Character Timeout controls the maximum duration between received characters before
sending the characters to the network. Larger values may decrease the number of network
packets, but increase the amount of time to receive characters. Smaller values may
increase the number of network packets, but decrease the amount of time to receive
characters. The range is 1 through 65535.
Configuration Files
Configuration files contain all configuration settings for the Modbus gateway. When the
Modbus gateway settings have been configured you can save the settings using Vlinx
Manager. Existing configuration files can be Opened (from Vlinx Manager), which loads
them into the Modbus gateway. This allows the same configuration to be applied to
multiple Modbus gateways, or to reload a previously used configuration.
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4. Properties
Vlinx MESR9xx Modbus Gateway
Data/Parity/Stop
The number of Data bits, type of Parity and number of Stop bits selected define the
serial port parameters at which the Modbus gateway will operate. These parameters must
be configured to match the parameters set on the Modbus network connected to the
Modbus gateway's serial port.
Data Bits controls the number of bits of data in each character. Options include 5, 6, 7 or
8 data bits.
Parity controls the error checking mode. Options are No Parity, Odd, Even, Mark or
Space.
Stop Bits controls the number of bits to indicate the end of a character. Options include
1, 1.5 and 2. (1.5 bits is only valid when 5 data bits is selected, which is rare. The 2 stop
bits setting is only valid when 6, 7 or 8 data bits is selected.)
Default Gateway
The Default Gateway address sets the default route to remote networks, enabling users
to access the Modbus gateway from outside the local network.
DHCP
DHCP (Dynamic Host Configuration Protocol) is a protocol used on special servers
that supply IP addresses to network nodes on request.
When DHCP is enabled on the Modbus gateway (factory default), on power up it sends a
DHCP request to the DHCP server, which assigns a dynamic IP address, subnet mask,
and default server to the Modbus gateway.
When DHCP is disabled (static IP addressing), the IP Address, Subnet and Default
Gateway fields must be set manually by entering the appropriate addresses in these fields.
If you do not know what addresses to use in these fields, ask your network administrator.
Notes:
A dynamic address assigned by the DHCP server may change if the server loses the Ethernet
connection or power is removed. If a device on the network that normally communicates with the
Modbus gateway is configured to communicate with a specific IPaddress of the Modbus gateway,
and the IP address has been changed, the device will not be able to communicate with the Modbus
gateway. Therefore, disabling DHCP and using a static IP address is recommended.
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4. Properties
Vlinx MESR9xx Modbus Gateway
If a DHCP server is not found on the network, the Modbus gateway automatically configures to an
IP address in the range of 169.254.0.0 through 169.254.255.255 and a subnet mask of 255.255.0.0
MESR9xx Modbus gateways come from the factory with DHCP enabled.
Firmware Version
The Firmware Version number (Vx.x.x) indicates the Modbus gateway's currently
loaded firmware release. From time to time new firmware is made available and can be
uploaded into the Modbus gateway using Vlinx Manager.
Hardware Version
The Hardware Version number of the Modbus gateway hardware is displayed on the
Login page of Vlinx Manager.
ID Routing
ID routing allows the gateway to manage slave device IDs between various Modbus
interfaces. By filling in the user defined slave ID table, a Modbus Gateway routes
requests to the correct serial port. One connection can command serial slaves on multiple
serial ports.
By filling in the drop down menu of ports with slave devices attached, adding IP
addresses of slaves, up to 10 address ranges can be routed.
By default all boxes are unchecked, the drop down menu is set to serial port one, and all
fill in boxes are blank.
IP Address
Software or hardware attempting to access the Modbus gateway via the network must
know the IP Address of the server. If DHCP is selected, the Modbus gateway requests
and receives a dynamic IP address from a DHCP server when it first connects to the
network. If DHCP is not selected you must type in a static IP address when configuring
Network settings (on the Vlinx Manager Network page). The static IP address remains
the same each time the server is powered up or starts/restarts.
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4. Properties
Vlinx MESR9xx Modbus Gateway
MESR9xxModbus gateways come from the factory with a default static IP address of
192.168.0.1, but will be reconfigured automatically via DHCP as appropriate.
If you need to change the static IP address and do not know what address to use, consult
your network administrator.
Link Status
Link Status of the currently selected Modbus gateway is shown on the Login page of
Vlinx Manager. Link status indicates the type of Ethernet connection between the
computer and Modbus gateway. It will either display 10BaseT or 100BaseTX in full
duplex or half duplex. Link status is dependant on the LAN, switches, hubs used in the
LAN topology.
MAC Address
The MAC Address is a hardware level address of the Modbus gateway that cannot be
changed. It is assigned in the factory. Every Ethernet device manufactured has it own
unique MAC address. The MAC address of each Modbus gateway is printed on the
device's label. The MAC address of the currently selected Modbus gateway is also
displayed on the Login page of Vlinx Manager.
Modbus Priority
This allows the gateway to move high priority messages to the front of the serial message
buffer. The priority can be based on the originating IP address, the Modbus ID, the
Modbus function code, or any combination of the three. Up to five different priorities
can be set.
The default will have all the check boxes unchecked and all the fill in boxes blank.
Modbus Serial Retries
This is the maximum number of times that the Modbus gateway will retry to send a
Modbus message to a Modbus client, before reporting a 0Bh exception if it is selected.
This should be limited to between 0 and 5.
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4. Properties
Vlinx MESR9xx Modbus Gateway
Modbus ASCII
The Modbus ASCII message protocol is a human readable version of the Modbus
message, and is one of the three Modbus formats supported by the MESR9xx Modbus
Gateway.
A major advantage of Modbus ASCII is it allows up to a 1 second gap between bytes. It
uses a Longitudinal Redundancy Check (LRC) checksum to verify message accuracy.
Modbus Message Buffering
The MESR9xx has two Modbus serial buffers, one for each serial port. Each will buffer
up to 32 Modbus messages. These buffers help ensure messages don’t get lost in a data
traffic jam, and are part of what makes Modbus such an outstandingly reliable serial
protocol.
Modbus Message Timeout
Message timeout is supported by the MESR9xx. This is the maximum amount of time
before a response to a message is expected.
Modbus RTU Message
The Modbus RTU message is broken into 4 different parts. The address field, the
function code, this is copied directly over from the Modbus TCP message, the data and
the error check, a 16 bit cyclic redundancy check or CRC.
Modbus Serial Control
Message Timeout
The message timeout is the maximum time the gateway allows for a response from the
slave device. The default is 1000ms.
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4. Properties
Character Timeout
Vlinx MESR9xx Modbus Gateway
The character timeout is the maximum time the gateway allows between characters from
the slave device, used only in RTU mode. The default is 10ms.
CRC/LRC Error Check
The CRC/LRC check calculates the CRC/LRC for the message received, and compares
this to the CRC/LRC with the message. If not the same the message is rejected.
Message Retries
Message retries is the number of times the gateway resends the message if it gets a
character timeout or CRC/LRC error. The default is two.
Modbus TCP Message
The Modbus TCP message may be broken up into multiple different TCP frames. The
Modbus TCP message contains three main blocks to the Modbus TCP message. The first
is the MBAP header. It describes the Modbus message, including the Transaction
Identifier, Protocol Identifier, Length and Unit ID. The second part is the Function Code.
The third is the Data. The Function Code and Data are the standard Modbus PDU.
Model
The Model number of the currently selected Modbus gateway is displayed on the Login
page of Vlinx Manager.
Network Mode
The network mode is the method used to configure the network parameters. It is either
“DHCP” or “Static IP”.
Network Protocols
Network Protocols available for use on MESR9xx Modbus gateways include TCP.
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4. Properties
Vlinx MESR9xx Modbus Gateway
Password
When you first receive the MESR9xx Modbus gateway from the factory the Password is
blank so that you can initially access the Modbus gateway without entering a value into
this field. To ensure security you should create and save a password the first time you
configure the Modbus gateway. After a password has been set up it must be entered each
time you login to Vlinx Manager. The password is used to access the configuration pages
from the Vlinx Manager Login page and can be changed from the General page.
Port# ID Remap
This allows the gateway to remap the Modbus ID to another ID on the serial port. This
would be used when there are two identical Modbus serial networks talking to Modbus
TCP controllers.
The first box is the staring ID of a range you want to remap; the second box is the last ID
of that range. If you are just remapping one ID the second box is not filled in. The third
box is the start of the remap range on the serial port. The fourth box will auto fill in
based on the range filled in the first 2 boxes. The range must check to make sure it is a
valid range, and does not overlap with any of the other ranges set. Up to 5 address ranges
can be remapped per port.
The default will have all the check boxes unchecked, and all fill in boxes blank.
Serial Interface Modes
Four serial interface modes of operation are:
• RS-232 - Point-to-point serial communications connection used by PC COM ports
and many other systems. Capable of baud rates up to 115.2 kbaud over short
distances (typically 50 feet). Typically uses DB-9 connectors but terminals are
also used on MESR9xx Modbus gateways.
• RS-422 - Point-to-point communications using a transmit pair and a receive pair.
RS-422 can operate at higher speeds and longer distances than RS-232. Typically
uses two shielded twisted pairs and screw terminals but DB-9 connectors are also
used on MESR9xx Modbus gateways.
• RS-485 2-wire - Similar speed and distance specifications as RS-422 but allows
multidrop connections. Typically uses one shielded twisted pair and screw
terminals but DB-9 connectors are also used on MESR9xx Modbus gateways.
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4. Properties
Vlinx MESR9xx Modbus Gateway
• RS-485 4-wire - Similar speed and distance specifications as RS-422 but allows
multi-drop and full duplex connections. Typically uses two shielded twisted pairs
and screw terminals but DB-9 connectors are also used on MESR9xx Modbus
gateways..
Select the appropriate serial interface mode for the type of connection between the
Modbus gateway's serial port and the device connected to it.
Note: Refer to the Appendix D for connector and pin-out details.
Modbus Gateway Name
Modbus Gateway Name is a unique name assigned to the Modbus gateway. It must be a
valid hostname as defined by RFC-952 and RFC-1123. The rules are:
• It must consist only of the characters "A" to "Z", "a" to "z", "0" to "9" or "-"
• It can start or end with a letter or a number, but it must not start or end with a "-".
• It must not consist of all numeric values.
Gateway Serial Port Number
The Gateway Serial Port Number of the currently selected port is shown in this field.
• MESR901-x Modbus Gateways feature one serial port.
• MESR902D-x and MESR902T-x Modbus Gateways feature two serial ports.
Subnet Mask
The Subnet Mask specifies the network mask the Modbus gateway uses when on a
subnetted network.
• For a Class A network (IP addresses 0.0.0.0 through 127.255.255.255) the default
subnet mask is 255.0.0.0.
• For a Class B network (IP addresses 128.0.0.0 through 191.255.255.255) the
default subnet mask is 255.255.0.0
• For a Class C network (IP addresses 192.0.0.0 through 233.255.255.255) the
default subnet mask is 255.255.255.0
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4. Properties
Vlinx MESR9xx Modbus Gateway
• For a Class D network (IP addresses 224.0.0.0 through 239.255.255.255) and
Class E Networks (IP addresses 240.0.0.0 through 255.255.255.255) the subnet
mask is ignored.
• MESR9xxModbus Gateways come from the factory with a default subnet mask
value of: 255.255.255.0
TCP (Transmission Control Protocol)
TCP (Transmission Control Protocol) provides reliable connection-oriented network
communication with error checking. In TCP mode the Modbus gateway can be
configured as a client or a server.
When the Modbus gateway is configured as a TCP client it initiates connections with a
server on the network. You must set up the IP address and port number of the server that
you want the client (Modbus gateway) to communicate with. You also select whether the
Modbus gateway is to connect at power up or only when it receives data from the device
connected to its serial port.
When the Modbus gateway is configured as a TCP server it waits for connections to be
initiated by another network device. You must set up the TCP port number that it will
listen to for connections and set the maximum (up to eight) number of simultaneous
connections it will accept. You can filter the connections it will accept based on specific
IP addresses or ranges of IP addresses that you specify.
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5. Upgrading Firmware
Vlinx MESR9xx Modbus Gateway
5. Upgrading the Modbus Gateway
Firmware
Occasionally, updated firmware may become available for your Modbus gateway. The
firmware can be upgraded using the Zlinx Manager software. The following procedure
describes the firmware updating process:
1. Click the Upgrade button to open the Firmware Upgrade dialog box.
Figure 20.
Firmware Upgrade Dialog Box
The name of the currently selected Modbus gateway appears in the top drop down
list. Other Modbus gateways (that have already been discovered) can be selected from
the drop down list, if desired.
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5. Upgrading Firmware
Vlinx MESR9xx Modbus Gateway
The current firmware version of the selected Modbus gateway is shown in the text
below the Modbus gateway name.
Information about the selected firmware file is shown in the third text box.
Downloading Firmware Files
The Firmware File list (second box) displays all firmware files in the firmware
installation folder. Only firmware that is compatible with the selected Modbus gateway is
available in this list.
To download the latest firmware files from an FTP site on the Internet:
1. Click the Internet button at the bottom of the window.
The Vlinx Manager connects to an FTP server on the Internet.
2. Click the Check for Updates button.
Progress Bar and Progress Box display information about and progress of the
download.
To download the latest firmware files from a file:
1. Click the Browse button to open an Open File dialog box.
2. Browse to the drive and folder containing the firmware file.
3. Select and download the file to the local firmware folder.
Uploading the Firmware to the Modbus Gateway
To upgrade the firmware:
1. In the Modbus Gateway Selection drop down list, select the Modbus gateway to be
upgraded.
2. In the Firmware Description drop down list, select the firmware to upload to the
Modbus gateway.
3. Click the Upgrade button.
Progress Bar and Progress Box provides information on the progress of the transfer.
4. In the Firmware File drop down list, select the firmware file to upload to the Modbus
gateway.
5. Click Upgrade.
The Progress box and Progress bar display information on the upgrading process.
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5. Upgrading Firmware
Vlinx MESR9xx Modbus Gateway
6. When the upgrade process is complete, click Close.
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6. Diagnostics
Vlinx MESR9xx Modbus Gateway
6. Diagnostics
Clicking the Diagnostics icon opens the Diagnostics dialog box and enables you to
check the operation of connected Modbus gateways on the local computer.
The Computer Information box displays information about the type of network
connections, the IP addresses, Subnet Masks and Default Gateways in use.
Figure 21.
Diagnostics Dialog Box
Testing a Modbus Gateway Connection
To run diagnostics on a Modbus gateway:
1. Click the Diagnostics icon.
The Diagnostics dialog box appears.
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6. Diagnostics
Vlinx MESR9xx Modbus Gateway
2. In the drop down box select the specific Modbus gateway you want to check.
3. Click the Start button
Information about the progress of the pinging process is displayed in the Test
Progress box.
Figure 22.
Testing a Modbus Gateway Connection
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7. Application Examples
Vlinx MESR9xx Modbus Gateway
7. Application Examples
Modbus gateways can be used to integrate Modbus networks in a wide variety of settings.
But as each setting has its own requirements, users may not understand how a gateway
helps, or if it’s appropriate for their specific needs.
The following scenarios are examples only, and many others are possible. Contact B&B
Electronics technical support for information on other applications.
From Serial Master to Modbus Gateway, Slave IDs Configurable
4. The original system consists of Gateways controlling serial slave devices:
Figure 23.
Direct IP Connection
The MESR Modbus gateway module connects serial slaves, so Ethernet SCADA masters
can control these. As slave IDs must be unique in a single system, these must be changed
to have them function on one network:
Figure 24.
SCADA to Slaves, IDs Configurable
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7. Application Examples
Vlinx MESR9xx Modbus Gateway
From Serial Masters To Ethernet Master, Slave IDs Fixed
Legacy Modbus slaves may have fixed IDs. To integrate these into a Modbus TCP
network, a multiport MESR model (List here) can assign virtual slave IDs. For
information on virtual slave IDs, see (list reference):
Figure 25.
Scada to Slaves, IDs Fixed
Keep Serial Master, Add Ethernet Master(s)
In this scenario, the control system is a direct, time-critical serial system. The serial
master must not be replaced, but Ethernet masters will need to have access to the serial
slaves for monitoring or supervision.
Figure 26.
Time Critical Control System
A sophisticated Modbus gateway (MESR921 or MESR922) can connect to the devices,
with slaves going to one link and master another. The gateway allows communication
between slaves and master, with a redirector aspect that lets the serial master keep on
communicating with the slaves.
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7. Application Examples
Vlinx MESR9xx Modbus Gateway
Figure 27.
Time Critical Control, Direct and Remotely Monitored
Modbus RTU, ASCII, and TCP Integration
The range of potential devices and configurations of Modbus serial networks is huge.
While simple serial meters are most common, complex manufacturing machines or PLC
controllers are also possible.
Integration of these devices may involve dealing with different serial environments. One
system’s baud rate may differ, or use Modbus ASCII instead of RTU. MESR protocols
makes it possible for differing Modbus systems to combine into one network, regardless
of technology or communication differences.
Figure 28.
Complex Modbus Network Integration Through Modbus Gateways
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8. Modbus Help
Vlinx MESR9xx Modbus Gateway
8. Modbus Help
Modbus ASCII/RTU Basics
The Modbus protocol emerged in the mid-1970s as an early protocol for linking terminals
with Modicon PLCs using a master/slave (sometimes called a master/client) relationship.
A simple, open, message-based protocol, it caught on quickly and became a defacto
standard in the industry. It supports asynchronous point-to-point and multidrop
communications and can be used with a variety of serial interfaces (RS-232, RS-422, RS-
485, modems, etc).
The original Modbus specification included two possible transmission modes: ASCII and
RTU. Modbus RTU mode is the most common implementation, using binary coding and
CRC error-checking. Modbus ASCII messages, though somewhat more readable because
they use ASCII characters, is less efficient and uses less effective LRC error checking.
ASCII mode uses ASCII characters to begin and end messages whereas RTU uses time
gaps (3.5 character times) of silence for framing. The two modes are incompatible so a
device configured for ASCII mode cannot communicate with one using RTU.
All Modbus communications are initiated by Modbus masters using a polling
query/response format. The master can send broadcast messages (using a slave address of
0), which all slaves accept, but do not reply to. More commonly the master polls
individual slaves sequentially. In each poll it sends a message containing a device
address, followed by a function code, any data that maybe required, and an error check
field. The addressed slave responds with a similar message structure. Typically it repeats
back its address and the function code, and then sends a field indicating the number of
bytes of data it is sending, followed by the data and the error check field.
Slave addresses can range from 1 to 247. Function codes include several common ones
typically used in all applications, and additional ones that may be implemented in specific
cases. Common function codes include: Read Coil Status (01), Read Input Status (02),
Read Holding Registers (03) and Read Input Registers (04).
When a master sends a message to a slave it expects to receive a valid response within
certain length of time. If the slave does not receive the message, or if the slave receives
the message but an error is detected, it does not respond. If the slave cannot respond
appropriately for some other reason (e.g. it does not recognize the function code), it will
return a message containing an exception response.
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8. Modbus Help
Vlinx MESR9xx Modbus Gateway
Hints and Tips
A few simple suggestions that may assist you if your system is experiencing problems
include:
• Slowing down the polling rate may be helpful if power cycling doesn’t cure the
problem.
• A common misperception is that every serial network must terminate with a resistor.
While this was true of early serial network configurations, it’s typically the wrong
answer – call our technical support and verify if you’re an exception, at 815.433.5100
option 3.
A sometimes difficult problem is difference in grounding voltage between various network
locations. Stray voltage from lightning or other sources may also find its way onto the network.
These conditions make isolation necessary in many settings.
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9. Appendices
Vlinx MESR9xx Modbus Gateway
9. Appendices
This section includes the following Appendices:
• Appendix A: Default Gateway Settings
• Appendix B: Product Specifications
• Appendix C: Dimensional Diagrams
• Appendix D: Connector Pinouts
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Appendix A: Default Gateway Settings
Setting Default Value
Gateway Name TBD
Password password field is blank from factory
DHCP Enabled
Default 192.168.0.1, DHCP will reconfigure
as necessary
IP Address
Net Mask 255.255.255.0
Gateway 192.168.0.254
MAC Address Fixed - see bottom label
Firmware Version (Vx.x.x)
Hardware Version (Vx.x.x)
Port 1, 2
Serial port mode RS-232
Baud Rate 9600
Data bits
8
Parity None, Even, Odd, Mark, Space
Stop bits 1 & 2
Flow Control None
Protocol TCP
Serial timeout 0 seconds
Inter-character timer 0 ms
TCP port Port 1 = 4000
Port 2 = 4001
Max connection
1
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Appendix B: Product Specifications
This section includes the following specifications:
• General Specifications
• Controls, Indicators and Connector Specifications
• Serial Interface Specifications
• Network Specifications
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9. Appendices
Vlinx MESR9xx Modbus Gateway
General Specifications
Hardware and
included accessories
MESR901-x, MESR902D-x or
Device
CD
MESR902T-x Modbus gateway module
CD with Vlinx Manager software for
Windows 2000, 2003 Server/XP/Vista x32
232NM9 Null Modem Crossover Cable for
DTE to DTE connection
ERS35 one-meter length of steel 35mm
DIN Rail
Using Vlinx Manager via a serial
connection, (press Reset button to enter
Console Mode)
Optional Accessories
Configuration Options
Cable
Rail
Via serial port
Via network
Using Vlinx Manager via a Ethernet
connection
Using a standard web browser such as
Internet Explorer 6.0/7.0 or Firefox 1.5/2.0
Vlinx Manager for
Modbus gateway
configuration
Operating
Windows 2000, 2003 Server, XP, & Vista
x32
Software
Environment
-34 to 74 °C (-29 to 165 °F)
Temperature
Storage Temperature -40 to 85 °C (-40 to 185 °F)
Operating Humidity
10 to 90% non-condensing
Part 15 Class A
Certifications
FCC
CE
CISPR (EN55022) Class A
EN61000-6-1 Generic Standards for
Residential, Commercial & Light Industrial
EN61000-4-2 to 11 ESD, RFI, EFT,
Surge, and CI
Enclosure
Rating
IP30
Mounting
DIN rail mount (35 mm)
Dimensions, Medium
Case
Dimensions, Small
Case
1.2 x 4.5 x 6.2 in (2.8 x 11.4 x 15.7 cm)
1.2 in x 3.3 x 4.7 in (3.1 x 8.4 x 11.9 cm)
Power Supply
(External Supply
Required)
Voltage Requirements 10 to 48 VDC
MESR90x – 4.0W (Max)
Power Consumption
MESR92x – 6.0W (Max)
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Manual Documentation Number MESR9xx-4508m
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Controls, Indicators and Connector Specifications
Hold in for 0 to 2 seconds for hardware
reset
Hold in for 2 to 10 seconds for Console
Mode (Do a hardware reset or recycle
power to exit Console Mode)
Hold in for more than 10 seconds to
reset to factory defaults
Color = Green
Switches
Reset button
Serial LED
(one per port)
On = Port open
Blink = Data traffic
Color = Green
On = 100BaseTX
Off = 10BaseT
Indicators
Link LED
Blink = Data traffic
Color = Green
Ready LED
Blink (once per second) = System OK
Off = System NOT OK
10BaseT/100BaseTX
Ethernet
Single RJ-45F (8 pin)
SC fiber
ST fiber
SC connector
ST connector
ESR901-x: one DB-9M connector
ESR902D-x: Two DB-9M connectors
Connectors
Serial
ESR902T-x: Two pluggable lockable
5.08 mm terminal blocks
5.08mm 2-position pluggable, lockable
terminal block
DC Power
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Serial Interface Specifications
Mode Selection
RS-232 lines
RS-232/422/485 software selectable
TXD, RXD, RTS, CTS, DTR, DSR, DCD, GND
TXDA(-), TXDB(+), RXDA(-), RXDB(+), GND
Data(-), Data(+), GND
RS-422 lines
RS-485 lines (2 wire)
RS-485 lines (4 wire)
TXDA(-), TXDB(+), RXDA(-), RXDB(+), GND
75, 150, 300, 600, 1200, 2400, 4800, 7200,
9600, 14400, 19200, 28800, 38400, 57600,
115200, 230400
Baud Rates
Data Bits
Parity
5, 6, 7, 8
None, even, odd, mark, space
1, 1.5, 2
Stop bits
Flow control
RS-422/485 biasing
None, RTS/CTS, XON/XOFF
Auto 4.7K ohm pullups and pulldowns
Auto termination with thru hole resistor (user
supplied)
RS-422/485 termination
RS-485 data control
Auto control via MCU
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Network Specifications
Memory
Serial Memory
Network Memory
5300
10 K bytes per port
10 K bytes
I/P Port Addresses
Configuration setting in TCP Mode
MESR9xx update
8888
Network
Communications
Network Physical
Layer Standards
10/100 Mbps Auto-detecting 10BaseT or
100BaseTX
IEEE 802.3 auto-detecting & auto
MDI/MDX 10BaseT and 100BaseTX
TCP, IPv4, ARP, Telnet, HTTP 1.0,
ICMP/PING, DHCP/BOOTP
LAN
Ethernet
Protocols Supported
IP Mode
TCP
Static, DHCP or Auto IP
User definable
Connection Modes
Search
Server, Client,
Serial direct COM and Ethernet auto
search or specific IP
Firmware Upgrade
Character count
Timeouts
Via serial, Ethernet or auto web search
0 to 65535
Character
Modbus Message
Serial
0 to 65535 ms, default set at 10 ms
0 to 65535 ms, default set at 1,000 ms
0 to 65535 sec
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Appendix C: Dimensional Diagrams
Figure 29.
Page 47
Dimensional Diagram of an MESR901 Modbus Gateway (Note: Small Case Used for MESR901 Series Units)
Manual Documentation Number MESR9xx-4508m
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Figure 30.
Page 48
Dimensional Diagram of an MESR902T Modbus Gateway (Note: Small Case Used for MESR902 Series Units)
Manual Documentation Number MESR9xx-4508m
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Figure 31.
Page 49
Dimensional Diagram of an MESR921 Modbus Gateway, Left and Right Side Views (Note: Medium Case Used
for MESR921 and MESR922 Series Units)
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Figure 32.
Dimensional Diagram of an MESR921 Modbus Gateway, Bottom, Top, Back and Front Views (Note: Medium Case
Used for MESR921 and MESR922 Series Units)
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Appendix D: Connector Pinouts
MESR901-x Serial Port Pinouts
DB-9M Pin
RS-232
DCD
RXD
TXD
DTR
GND
DSR
RTS
CTS
RI
1
2
3
4
5
6
7
8
9
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Terminal
RS-422
TXA(-)
TXB(+)
RXA(-)
RXB(+)
GND
RS-485
DATA-
DATA+
---
A
B
C
D
E
---
GND
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9. Appendices
Vlinx MESR9xx Modbus Gateway
MESR902D-x Serial Port Pinouts
DB-9M Pin
RS-232
RS-422
RXA(-)
RXB(+)
TXB(+)
TXA(-)
GND
---
RS-485
---
1
2
3
4
5
6
7
8
9
DCD
RXD
TXD
DTR
GND
DSR
RTS
CTS
RI
---
DATA+
DATA-
GND
---
---
---
---
---
---
---
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9. Appendices
Vlinx MESR9xx Modbus Gateway
MESR902T-x Serial Port Pinouts
Terminal
RS-232
RS-422
TXA(-)
TXB(+)
RXA(-)
RXB(+)
GND
RS-485
DATA-
DATA+
---
A
B
C
D
E
RTS
TD
CTS
RD
---
GND
GND
In the RS-422 mode, TX lines are outputs and RX lines are inputs. Connect the Modbus
gateway TXB(+) line to the RXB(+) line of the Modbus network, and the Modbus
gateway TXA(-) to the RXA(-) of the Modbus network.
Ground is signal ground and provides a common mode reference for the RS-422 Receiver
and Transmitters.
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9. Appendices
Vlinx MESR9xx Modbus Gateway
Standard Ethernet Cable RJ-45 Pin-out
RJ-45 Pin
Signal
TX+
Wire Color
1
2
3
4
5
6
7
8
White-Green
Green
TX+
RX+
White-Orange
Blue
Not used
Not used
RX-
White-Blue
Orange
Not used
Not used
White-Brown
Brown
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10. Glossary
Vlinx MESR9xx Modbus Gateway
10. Glossary
Term Definition
ADU Application Data Unit
ASCII American Standard Code for Information Interchange
Baud Rate Number of bits per second
CRC Cyclical Redundancy Checking
Number of bits per byte, normally 7 with Modbus ASCII, and 8 with
Modbus RTU
Data Bits
DHCP Dynamic Host Configuration Protocol
EIR203 B&B’s 3 port Ethernet switch
B&B term for Ethernet port capable of quick stuff/no stuff option for copper,
Flexport single mode fiber of various distance and connector type, or mult-mode fiber
of various connector type
Flow Control The process of managing the rate of data transmission between two nodes.
Function Code A code field that tells the Gateway what kind of action to perform
Modbus
Gateway
A bridge to get from Modbus TCP to Modbus Serial
GUI Graphical User Interface
IP Internet Protocol
IPv4 Internet Protocol version 4
LED Light emitting diode. Used as a visual indicator
MBAP MODBUS Application Protocol
MEI Multi Electrical Interface via RS-232/422/485
MES1A B&B’s Ethernet Modbus gateway, RS-232 on serial port
MES1B B&B’s Ethernet Modbus gateway, RS-422/485 on serial port
B&B’s Ethernet Modbus gateway, Dual Ethernet ports, Dual serial ports
with MIE and terminal blocks
MESR922T
Modbus A request/reply protocol and offers services specified by function codes.
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10. Glossary
Vlinx MESR9xx Modbus Gateway
Term Definition
A binary digit that is added to ensure that the number of bits with value of
Parity Bit one in a given set of bits is always even or odd. It may also be a Mark (1), or
a Space (0).
PDU Protocol Data Unit
Interface between Data Terminal Equipment and Data Circuit-Terminating
Equipment Employing Serial Binary Data Interchange
RS-232
Electrical Characteristics of Generators and Receivers for Use in Balanced
Digital Point to Point Systems
RS-422
Electrical Characteristics of Generators and Receivers for Use in Balanced
Digital Multipoint Systems
RS-485
RTU Remote Terminal Unit
Number of bit times after a character is transmitted before the next character
can start transmission.
Stop Bit
TCP Transmission Control Protocol
Unit ID Unit Identifier. This is the same as the slaves address.
VESR B&B’s Second Generation Ethernet Gateway Line
Vlinx B&B’s family name for the Gateway line
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