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What is the Modbus address and Unit ID for my ION Meter

Issue
Confirming Modbus address and Unit ID

Product Line
ION Series Meters

Environment
Modbus

Cause
Determing Modbus specifications

Resolution
The Modbus address is dependant on how the meter and communication system is configured
1. If using Modbus TCP, the slave address, the meter default is ID 100. Since all Modbus TCP devices have unique IP addresses it allows the default to be used for all units.
2. If using serial Modbus protocol, the Modbus unit ID is the unit ID of the meter as configured on the relevant serial communication port.

Power PC based ION platforms intorduced the "Modbus Master Options Module" starting with firmware V350. This changes how the meter responds to modus requests:
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The default setting is GATEWAY DISABLED, which disables the gateway functionality
and allows the meter to respond to any Unit ID for Modbus TCP (port 502) or
Modbus RTU (port 7701) requests. This is different from the GATEWAY ENABLED setting, which sets the meter to respond only to Unit ID 255 and
enables the gateway functionality even if no downstream devices are setup.
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The above statements are excerpted directly from the "Modbus Gateway Connection" subsection of the "Modbus Master Options Module" section of the ION Reference document (p. 386 of 494).

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