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5 OPERATION IN THE MODBUS RTU NETWORK – SLAVE MODE
The CFW320 frequency inverter has the following characteristics when operated as a slave in Modbus RTU network:
Network connection via RS485 serial interface.
Address, communication rate and byte format defined by equipment parameters.
It allows the CFW320 frequency inverter programming and control via the access to parameters.
It allows accessing all the markers and data used in the ladder program of the CFW320 frequency inverter.
5.1 AVAILABLE FUNCTIONS
In the Modbus specification are defined the functions used to access different types of data. In the CFW320, in
order to access those data the following services (or functions) have been made available:
Code
01
02
03
05
06
15
16
22
23
43
5.2 MEMORY MAP
The frequency inverter CFW320 has different types of data accessible through the Modbus communication. These
data are mapped at data addresses and access functions as described in the following items.
5.2.1 Parameters
The CFW320 frequency inverter Modbus communication is based on the reading/writing of the equipment
parameters. All parameters of the equipment are available as 16-bit holding registers. The data addressing is
done with the offset equal to zero, which means that the parameter's network address (Net Id) corresponds to the
register address. The
Table 5.2 on page 20
holding register:
It is necessary to know the device list of parameters to be able to operate the equipment. Thus, it is possible to
identify what data are needed for the status monitoring and the control of the functions. The main parameters are:
Monitoring (reading):
P680 (holding register address 680): Status word.
OPERATION IN THE MODBUS RTU NETWORK – SLAVE MODE
Table 5.1: Supported Modbus Functions
Name
Read Coils
Read Discrete Inputs
Read Holding Registers
Write Single Coil
Write Single Register
Write Multiple Coils
Write Multiple Registers
Mask Write Register
Read/Write Multiple registers
Read Device Identification
illustrates the parameters addressing, which can be accessed as
Table 5.2: Parameters Access - Holding Registers
Parameter
P000
P001
. .
.
P100
. .
.
Description
Reading of bit blocks of the coil type
Reading of bit blocks of the discrete input type
Reading of register blocks of the holding register type
Writing in a single bit of the coil type
Writing in a single register of the holding type
Writing in bit blocks of the coil type
Writing in register blocks of the holding register type
Writing in holding register using mask
Reading and writing in register blocks of the holding
register type
Identification of the device model
Modbus data address
Decimal
Hexadecimal
0
0000h
1
0001h
. .
. .
.
.
100
0064h
. .
. .
.
.
CFW320 | 20
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