The Babel Buster MX-61-GW is a Modbus transparent pass-through gateway that transparently connects Modbus RTU devices to Modbus TCP and vice versa. All requests received from an RS-485 master are passed straight through to Modbus TCP servers. When configured to go the other way, all requests received from a TCP client are passed straight through to RS-485 slaves.

MX-61-GW Functionality

The MX-61-GW Modbus transparent pass-through gateway can be configured to connect multiple Modbus RTU RS-485 devices to a single IP address on the TCP network. Conversely, the MX-61-GW can be configured to connect multiple Modbus TCP devices to a Modbus RTU RS-485 network.

Feature Highlights
• Directly passes RTU messages to TCP
• Directly passes TCP messages to RTU
• Can map multiple RTU devices to single TCP IP address
• Can map multiple TCP devices as RTU slaves
• Configured via internal web server
• FCC/CE Mark
• Software Included, No Drivers to Buy

Babel Buster MX-61-GW Modbus Transparent Pass-Through Gateway

Babel Buster MX-61-GW Modbus Transparent Gateway

Order code: MX-61-GW
Retail price: $549.00

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Control Solutions’ Babel Buster® MX-61-GW is a non-mapping gateway used to directly route Modbus RTU messages to Modbus TCP and vice versa. This version of gateway does not do any data translation or remapping of registers, nor does it even look at the data being transferred. The MX-61-GW will satisfy your requirement for either of these two options:
   • Accessing multiple RTU devices from one or more TCP clients
   • Accessing multiple TCP devices from single RTU master

MX-61-GW network functionality

The Babel Buster MX-61-GW is a non-mapping Modbus gateway used to simply forward Modbus RTU requests and responses to Modbus TCP, and vice versa. Most Control Solutions gateways involve mapping, and the gateway itself contains registers or objects which hold copies of data found in other devices. This intermediate data buffering is what allows access to the same data from multiple protocols. The non-mapping gateway discussed here does not contain any of its own registers. It simply forwards whatever request it receives to the other side by simply repackaging and retransmitting exactly the same request.

The process of “repackaging” the Modbus request or response is illustrated below. The core of a Modbus data packet is the same for RTU and TCP. It contains a slave address (or unit number), a function code, and some data. The “data” is most often a starting register number, register count, and register data (if writing).

Comparison of Modbus TCP and RTU messages

The process of translating RTU to TCP or vice versa is simply a matter of adding or subtracting TCP header and RTU checksum. The only configuration required in this type of gateway is to create an association between RTU slave addresses and TCP IP addresses.

Accessing one or more Modbus RTU slaves from TCP with the external Modbus TCP device acting as client (master) means the gateway needs to act as an RTU master on the RTU network. Select “I act as the RTU master” for mode. You do not need to do anything on the TCP Device Map page for this mode.

Accessing one or more Modbus TCP server devices from an external Modbus RTU master means the gateway needs to act as one or more RTU slaves on the RTU network. Select “I act as one or more RTU slaves” for mode.

The gateway can present one or more TCP servers as one or more RTU slaves. There can be a one to one mapping, or a many to one mapping. The most common application will be a one to one mapping of RTU address to TCP address.

The TCP Device Map is where you establish your association between RTU address and TCP device IP address. When operating in this mode, if an RTU address is not found in this table, then the gateway will simply not respond. The expected behavior for RTU slave devices is that they remain silent if the request does not contain their address (aka slave ID or unit number). This gateway may be acting as multiple RTU slaves, but it will remain silent if the RTU address is not found in this table.

Configuration of the gateway is done via the secure web pages served by the internal web server. The user simply fills in templates. The entire configuration is saved in the internal Flash file system in XML format. This file may be exported to replicate additional copies of the configured device, or for backup.

Screen shot from MX-61-GW Modbus TCP to RTU Gateway

Click on the link below to view a demo copy of the entire Web UI in the MX-61-GW. This demo is actually the BB3-6101-GW, but the MX-61-GW is identical except for name and picture of product on home page.

 MX-61-GW Demo Web


MX-61-GW Features

• Modbus RTU Master or Slave
• Modbus TCP Client and Server
• Supported RTU baud rates: 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200
• Modbus TCP over Ethernet 10/100BaseT
• Up to 120 simultaneous TCP connections
• Full range of 1 to 247 RTU device addresses
• Configure via secure web pages with password protection
• Flash file system for XML configuration files
• Online help, Quick Help section at bottom of every web page
• Field upgradeable firmware upload via ftp
• DHCP or static IP address
• Hardened EIA-485 transceiver for Modbus RTU
• Powered by 10-30VDC or 24VAC 50/60 Hz
• Power Consumption: 0.1A @ 24VDC
• Panel mount, 70mm H x 131mm W x 38mm D
• Pluggable screw terminal block for power & RTU network
• Operating temperature -20°C to +75°C
• Humidity 5% to 90% non-condensing
• FCC Class A, CE Mark

MX-61-GW Video Library

Watch these videos for an introduction to configuring the gateway. It's easier than reading!

Introduction to the MX-61-GW Modbus Gateway

Our most extensive technical support is provided by the same engineering staff that developed the products. Your personal attention from this staff is available via the support ticket system.

No user/password is required to open a new ticket. Once you open a ticket, you will immediately receive an email with your ticket number. Your ticket number becomes your login to review your ticket(s) later. Click the Support Ticket icon anywhere you see it. (If you do not get an email with your ticket number, within minutes, check your junk folder, spam settings, etc, and try again if necessary.)

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