Enhanced Remote Device Connectivity via DeviceMaster Modbus Server!
Modbus protocol is widely used in the industrial control field due to its open and simple specifications, ease of use, excellent reliability, flexibility, real-time performance etc. Modbus modes and functions differ depending on cable type. Modbus/RTU and Modbus/TCP are some of the most common data formats of the Modbus protocols used in the industrial market place.
Modbus/RTU and Modbus/TCP Overview
- Modbus /RTU
Modbus/RTU is a native Modbus in hexadecimal format which includes the basic Modbus messages that contain simple read and write requests. The format is as follows:
The terms Master or Client are used to identify the server of the message.
The terms Slave or Server are used to identify the devices responding to the message.
- Modbus /TCP
Modbus/TCP is an Ethernet based protocol that contains a Modbus/RTU message, with the exception of the 2 byte CRC. The Modbus/TCP message contains a header with information designed to provide message identification and routing information. The format is as follows:
Modbus/TCP is used for connecting advanced Ethernet based devices, such as PLCs, HMIs, SCADA systems, and most OPC Servers to:
Other Ethernet devices supporting Modbus/TCP.
Remote serial Modbus/RTU devices through gateways (such as DeviceMaster UP Modbus)
Remote serial or Ethernet TCP/IP ASCII devices through a gateway (such as the DeviceMaster UP Modbus)
- Modbus /RTU over Ethernet TCP/IP
Modbus/RTU can be used for Ethernet TCP/IP socket connections. This is not the same as Modbus/TCP, however it provides a very simple method of interfacing to remote devices. Typically, Modbus/RTU is used for serial port connectivity. However, the Modbus/RTU message can be also packetized by TCP/IP header to provide Ethernet remote accessibility and more flexible application.
[For Modbus/TCP functionality refer to DeviceMaster UP Modbus series]
DeviceMaster Modbus Server for advanced Modbus/RTU over
Ethernet TCP/IP to serial device connectivity
Combined with Ethernet technology, Modbus Server firmware of Comtrol’s DeviceMaster provides advanced usage for Modbus/RTU over Ethernet TCP/IP.
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Through standard Ethernet TCP/IP, per each serial port it is possible to connect up to six master applications with different IP addresses by Modbus Server.
This is a huge breakthrough for only single Master on traditional Modbus/RTU communication.
Besides, although users make their Modbus/RTU connections ready in the beginning, they still need to maintain the whole system data transmission quality. With detailed diagnostic capability of Modbus Server, users can easily get sufficient information from the overall message statistics in the web pages. Even a serial log is also included to provide message level diagnosis. |
Therefore, this unique software not only greatly enhances system maintenance capabilities, but it also provides Mudbus/RTU making the DeviceMasters series to become a suitable solution for those applications and OPC servers, where Modbus/TCP is not available, but which require Modbus/RTU functionality, such as building automation, factory, warehouse, and transportation.
Note: The used communication method of Modbus/RTU over Ethernet TCP/IP is PC based, not PLC based. For PLC based Modbus/TCP functionality, please refer the DeviceMaster UP Modbus.
Modbus/RTU multi-connections over Ethernet TCP/IP
Without using standard Modbus gateway for Modbus/RTU to Modbus/TCP conversion, Modbus Server can be easily uploaded on most of Comtrol’s DeviceMaster Ethernet gateways to take advantage of Ethernet multi-connectivity features for Modbus RTU communication. It supports Modbus/RTU over Ethernet TCP/IP connections to the corresponding serial port via intelligent Modbus message routing for some specific applications.
The multi-connection functionality of the firmware greatly benefit users:
Supports up to six Ethernet TCP/IP connections to each serial port.
>> One TCP/IP connection can be created with the “Connect To” connection method.
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The “Listen” connection method accepts up to five or six connections, depending if the “Connect to “ connection is active.
Combined with a serial port redirector, can support up to six COM port connections to each serial port
Supports up to 255 Modbus slave devices per port. Both valid (1-247) and reserved (248-255) device ids
are supported.
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Distinguished Performance & Message Diagnostics
To maintain the high-quality of system communication, Modbus Server is designed for comprehensive device and port specific diagnostic web pages that display status, message response timing, timeout and error counts as well as overall message statistics. It provides:
Modbus/RTU specific message handling:
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CRC verification of all messages received on the TCP/IP and serial interfaces.
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Timing out of responses from slave Modbus/RTU devices.
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Broadcast message handling on connected port only.
System monitoring to ensure gateway operation:
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Gateway busy.
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Application message timeouts.
Advanced diagnostics web pages:
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Modbus device specific statistics, response timing and status.
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Up to 255 devices per serial port can be monitored simultaneously.
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Serial port specific statistics and status.
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Serial port message logging. .
To get more information, on DeviceMaster UP Modbus series Industrial Ethernet Gateways, please Click here!!
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