Configuring a large number of Modbus devices can be arduous. Unlike Ethernet switches, where routing is accomplished automatically through an ARP table, the routing mechanism for Modbus gateways with multi-serial ports is much more complicated. The main purpose of a routing table is to indicate which Modbus device (slave ID) is connected to which serial port on a gateway. Once a gateway receives a Modbus request for a specific Modbus device, it can dispatch this request via the referring routing table to the serial port that connects to the target Modbus device. The routing table needs to be maintained for troubleshooting and maintenance; however, creating and managing a routing table is laborious.
The Dilemma of Handling a Large Number
of
Modbus Devices
The widespread adoption of the industrial Internet of Things (IIoT) has connected a massive number of serial devices to the Internet. However, configuring and handling multiple serial devices can be a herculean task. Take data centers, for example, where hundreds to thousands of serial-based Modbus meters communicate via the Modbus RTU protocol. These meters also need to be monitored and controlled in a control room, which uses Modbus TCP protocol. To transmit data from serial to Ethernet and convert Modbus RTU to Modbus TCP, a high-port-density Modbus gateway is usually the best option for connecting a large number of serial devices to a control room. However, more time and effort are required to plan and manage a lot of Modbus devices with regard to topology and connectivity. Moreover, engineers have to deal with possible connectivity errors when dispatching a large number of Modbus requests to serial devices that are connected to a Modbus gateway.
