Modbus Rtu; Introduction; Node Address Setting - Lenze i55AE125B Manual

Configuring the network

Modbus RTU

Introduction

9.5 Modbus RTU
Modbus is an internationally approved, asynchronous, serial communication protocol,
designed for commercial and industrial automation applications.
Detailed information on the Modbus can be found on the web page of the international
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Modbus Organization, USA, who also further develop the Modbus protocol: http://
www.modbus.org
Information about the dimensioning of a Modbus network can be found in the configura-
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tion document for the inverter.
Preconditions
Control unit (CU) of the inverter is provided with Modbus.
9.5.1 Introduction
The process of data transmission distinguishes between three different operating modes:
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Modbus ASCII, Modbus RTU, and Modbus TCP. This chapter describes the Modbus RTU
operating mode ("Remote Terminal Unit").
The Modbus protocol is based on a master/slave architecture where the inverter always
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works as slave.
The Modbus network only permits one master sending commands and requests. The mas-
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ter is also the sole instance to be allowed to initiate Modbus communication. No direct
communication takes place between the slaves.
The physical interface corresponds to TIA/EIA-485-A which is very common and suitable
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for the industrial environment. This interface enables baud rates from 2400 to
115200 kbps.
The inverter supports Modbus function codes 3, 6, 16 (0x10) and 23 (0x17).
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9.5.2

Node address setting

Each network node must be provided with a unique node address.
The parameters for the baud rate of the device are described below.
The parameters for addressing the device are described below.
Details
The node address of the inverter can be optionally set in
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the DIP switches on the device labelled with "1" ... "128".
The setting that is active when the inverter is switched on is the effective setting.
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The labelling of the DIP switches corresponds to the values of the individual DIP switches
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for determining the node address (see the following example).
The node address 0 is reserved for messages to all nodes ("Broadcast") .
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The active node address is shown in
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Example of how the node address is set via the DIP switches
DIP switch
Setting
Value
Node address = sum of all values = 16 + 4 + 2 + 1 = 23
Parameter Name / value range / [default setting]
0x2321:001 Modbus settings: Node ID
(P510.01) (Modbus sett.: Node ID)
1 ... [1] ... 247
282
0x2322:001 (P511.01).
128 64 32
OFF OFF OFF
0 0 0
0x2321:001 (P510.01) or using
16 8
ON OFF
16 0
Info
Optionally setting of the node address (instead of setting via DIP
switches 1 ... 128).
• The node address set here only becomes effective if DIP switches
1 ... 128 have been set to OFF before mains switching.
• A change in the node address only becomes effective after a restart of
Modbus communication.
4 2 1
ON ON ON
4 2 1