9.5 Modbus RTU
Modbus is an internaonally approved, asynchronous, serial communicaon protocol,
designed for commercial and industrial automaon applicaons.
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Detailed informaon on the Modbus can be found on the web page of the internaonal
Modbus Organizaon, USA, who also further develop the Modbus protocol: hp://
www.modbus.org
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Informaon about the dimensioning of a Modbus network can be found in the congura-
on document for the inverter.
Precondions
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Control unit (CU) of the inverter is provided with Modbus/CANopen.
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Modbus/CANopen selector at the inverter front is set to "Modbus".
9.5.1 Introducon
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The process of data transmission disnguishes between three dierent operang modes:
Modbus ASCII, Modbus RTU, and Modbus TCP. This chapter describes the Modbus RTU
operang mode ("Remote Terminal Unit").
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The Modbus protocol is based on a master/slave architecture where the inverter always
works as slave.
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The Modbus network only permits one master sending commands and requests. The mas-
ter is also the sole instance to be allowed to iniate Modbus communicaon. No direct
communicaon takes place between the slaves.
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The physical interface corresponds to TIA/EIA-485-A which is very common and suitable
for the industrial environment. This interface enables baud rates from 2400 to
115200 kbps.
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The inverter supports Modbus funcon codes 3, 6, 16 (0x10) and 23 (0x17).
Conguring the network
Modbus RTU
Introducon
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