7EN02-0390-03

Modbus Ethernet gateway implementation

There are some specific aspects to your meter’s Modbus Ethernet gateway implementation.

A Modbus request is sent through Ethernet using Modbus/TCP to the gateway meter. If this request is addressed with the slave ID of one of the downstream serial devices, the meter forwards the message to that device using Modbus RTU. When the downstream device responds, the gateway meter forwards the response back to the Modbus master. In addition to Modbus slave addresses 1 - 247, the Modbus gateway supports slave address 255, which sends a Modbus request to the gateway meter only.

For Modbus gateway, you must install the serial Modbus slave devices, configure them and connect them to your Ethernet-connected Modbus gateway meter. Ensure that each serial device is configured to communicate over Modbus with the same baud rate and has a unique unit ID. Configure the gateway meter’s serial port to use the Modbus master protocol and enable the Modbus gateway feature, create a Modbus gateway site in ION Setup or an energy management system, and add the serial devices to the Modbus gateway site.

NOTE: Modbus Ethernet gateway supports up to 32 Modbus TCP connections.
Related topics: “Configuring a Modbus gateway using ION Setup” See “Protocols and ports” for the maximum number of Modbus TCP connections for your device.

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