MGate MB3660 Modbus Gateway
Introduction
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Overview
The MGate MB3660 (MB3660-8 and MB3660-16) Series comprises redundant Modbus gateways that convert
between Modbus TCP and Modbus RTU/ASCII protocols. They can be accessed by up to 256 Modbus TCP client
(master) devices, or connect to 128 Modbus TCP server (slave) devices. The MGate MB3660 isolation model
provides 2 kV isolation protection suitable for power substation applications. The MGate MB3660 gateways are
designed to easily integrate Modbus TCP and RTU/ASCII networks. The MGate MB3660 gateways offer features
that make network integration easy, customizable, and compatible with almost any Modbus network.
For large-scale Modbus deployments, MGate MB3660 gateways can effectively connect a large number of
Modbus nodes to the same network. The MB3660 Series can physically manage up to 248 serial slave nodes for
8-port models or 496 serial slave nodes for 16-port models (the Modbus standard only defines Modbus IDs from
1 to 247). Each RS-232/422/485 serial port can be configured individually for Modbus RTU or Modbus ASCII
operation and for different baudrates, allowing both types of networks to be integrated with Modbus TCP
through one Modbus gateway.
High Performance with Innovative Command Learning
The MGate MB3660 gateways support two communication modes: transparent mode and agent mode. For
transparent mode, the gateway converts Modbus commands from Modbus TCP to Modbus RTU/ASCII, and vice
versa, or from serial Master to serial Slave. However, since only one Modbus protocol request-response action
can be executed at any given time, each Modbus device has to wait its turn, resulting in poorer performance.
Agent mode is designed to overcome this performance weakness. By allowing users to manually key in Modbus
commands, the gateway can send Modbus commands to multiple Modbus devices at the same time. Since the
gateway actively and continuously retrieves data from Modbus devices simultaneously through the different
serial ports, users will see a dramatic reduction in the amount of time a Modbus device needs to wait to be
accessed. SCADA systems can retrieve Modbus device data directly from the gateway’s memory, instead of
waiting for the gateway to pass commands to the serial ports, enhancing the Modbus gateway’s communication
performance.
Transparent mode helps users adopt existing SCADA programs, but with reduced communication performance,
whereas agent mode is characterized by high performance, but it requires users to go through the trouble of
keying in Modbus commands. In order to provide better performance, without requiring users to key in a lot of
Modbus commands, the MGate MB3660 gateways are designed with an innovative Command Learning function,
which can be activated with a single mouse click. Once activated, the gateway will learn and memorize the
Modbus commands it receives, and once a command has been learned, the gateway will act as though it were
in agent mode and actively send Modbus requests to the relevant Modbus devices. Since the data is saved in
a different memory space that can be accessed by the SCADA system, the SCADA system can retrieve Modbus
response data directly from the gateway’s memory, instead of waiting for the data to pass through the Modbus
devices, dramatically increasing communication performance.
Windows-Based Utility and Web Console for Easy Setup
A Windows-based utility is provided to make it easy to search for and locate devices, assign IP addresses,
import/export configuration files, and upgrade the the MGate MB3660’s firmware. The utility automatically
connects to all available MGate MB3660 units on the LAN. A user-friendly web console is provided to configure
the device from a web browser.
