Schneider Electric iEM3300 Communications via Modbus RS-485, Modbus communication overview

iEM3100 / iEM3200 / iEM3300 series user manual Communications via Modbus RS-485

Chapter 5 Communications via Modbus RS-485

What is in this chapter?

This chapter contains the following sections:

Modbus communication overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Modbus functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Command interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Modbus register list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 Read Device Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Modbus communication overview

Modbus RTU protocol is available on the iEM3150, iEM3155, iEM3250, iEM3255, iEM3350 and iEM3355.

The information in this section assumes that you have an advanced understanding of Modbus communications, your communications network and the power system that your meter is connected to.

There are three different ways of using Modbus communication:

•by sending commands using the command interface (see “Command interface overview” on page 53)

•by reading the Modbus registers (see “Modbus register list” on page 57)

•by reading Device Identification (see “Read Device Identification” on page 61)

Modbus communications settings

Before communicating with the device using Modbus protocol, use the display to configure the following settings:

Settings	Possible values
	9600 Baud
Baud rate	19 200 Baud
	38 400 Baud
	Odd
Parity	Even
	None
	NOTE: number of stop bits = 1
Address	1–247

Communications LED indicator for Modbus devices

The yellow communications LED indicates the status of communication between the meter and the master as follows:

If...	Then...
The LED is flashing	Communication with the device has been established.
	NOTE: If there is an error online, the LED also flashes.
The LED is off	There is no active communication between the master and the slave

Related topics

•For more information on the Modbus protocol, see the Modbus organization website at www.modbus.org.

•See “Hardware overview” on page 16 for the location of the communications LED.

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