As more industrial applications are using industrial networking protocols, Modbus TCP are gaining a lot of popularity. Modbus TCP provides centralization and real-time update to improve response time and reduce operational costs. Modbus TCP is one of the most popular industrial Ethernet protocols due to the fact that it is openly published and easy-to-deploy. Modbus TCP use the same master-slave technique as the regular Modbus RTU or Modbus ASCII, where the master sends a request to the slave, and slave feeds data back to the master in a continuous cycle.
By using a Modbus Ethernet Gateway it allows the communication from Modbus TCP to Modbus RTU or Modbus ASCII, with a very simple setup and programing you will have your Modbus master or Modbus slave converted to Modbus TPC, now you have broken the limit or running RS485 cable, and move to the Modbus TCP so you can enjoy the flexibility of communication through Ethernet .
The things you should look for in the Modbus Ethernet Gateways
Since the old Modbus is running RS485, so you want to look for a gateway that will support the number of clients or hosts that you have on the RS485 network. As a Modbus gateway for slave device, the gateway should allow administrators to collect data from several masters simultaneously. As a Modbus gateway for master device, it should bridges multiple slave devices and enable communication among these services.
Intelligent Prioritize Mechanism
The priority of a request can be determined by the Modbus TCP command function code, slave ID, or IP address/TCP port. In a network connection where multiple requests are made from several devices, the gateway can be setup to filter a specific Modbus TCP command as urgent and has priority and send it to the front of the queue, such as an urgent “suspend” command to stop a drive. Administrators could also assign the highest priority to a specific slave ID because that slave device transmits important I/O signals related to the safety of the system.
Exception Notification via Relays
For urgent hardware issues, such as power supply and network connection events, the best way to receive notification is through a relay output for on-site troubleshooting. The administrator can use this relay output to control the I/O to turn on the alarm in the event of an error. In addition, for reliability, the gateway should support dual power inputs—the first input being the main power supply and the second one being the backup power supply (such as battery power). When the main power supply fails, the battery supplies the gateway enough power to signal to the administrator that the main power supply has failed. Another frequent hardware issue is the Ethernet link. Factors such as the quality of cables and connectors, and even the Ethernet switch, may cause disconnection. The gateway should be able to notify the administrator as soon as this happens before the problem affects the entire operation.
Like most network devices, the Modbus Ethernet Gateway provides an event log for troubleshooting, recording important events such as unauthorized access or login failures, network problems, protocol issues, and power cycles or system reboots. When the gateway undergoes power cycling, possibly due to firmware issues, the gateway must record the event to facilitate troubleshooting.
Console or Utility Tool
You may encounter issues with protocol settings from the start while installing and configuring the gateway. Using the wrong slave ID, wrong data address, or even incorrect baud rate will result in the inability to establish a connection between the gateway and the devices. In most cases, even after a connection has already been established, it is necessary to check whether the I/O data transferred between the networks is correct. You can validate data accuracy by changing the device I/O data and checking if the gateway shows the correct data or not. The gateway records all traffic information, and displays the latest I/O data with decoded information. Since these functions are quite complicated, it is useful to have a utility that shows detailed event information and provides a better user interface that can be used to investigate any number of issues.
With all the above on what you want to look for in your Modbus Ethernet Gateway, it will not only help you convert your current Modbus RTU/ASCII to Modbus TCP, and it also helps you monitor your Modbus TCP equipment, and help you troubleshoot when there is a problem in your network. You can also pick and choose what is most important to you and look for the Modbus Gateway that will meet your needs.
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