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iEM3100 / iEM3200 / iEM3300 series user manual Communications via Modbus RS-485
DOCA0005EN-04 51
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:
Communications LED indicator for Modbus devices
The yellow communications LED indicates the status of communication between the meter and the
master as follows:
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.
Settings Possible values
Baud rate
9600 Baud
19 200 Baud
38 400 Baud
Parity
Odd
Even
None
NOTE: number of stop bits = 1
Address 1–247
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