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MODBUS communications can perform the following operations regardless of the settings in b1-01 and b1-02.
Monitoring operation status from the PLC
•
Setting and reading parameters
•
Resetting errors
•
Inputting multi-function commands
•
An OR operation is performed between the multi-function commands input from the PLC and commands
input from multi-function contact input terminals S3 to S7.
Message Format
In MODBUS communications, the master sends commands to the slave, and the slave responds. The message
format is configured for both sending and receiving as shown below, and the length of data packets is changed
by the command (function) contents.
Slave address
Function code
The space between messages must support the following.
Slave Address
Set the Drive address from 0 to 32. If you set 0, commands from the master will be broadcast (i.e., the Drive
will not return responses).
Function Code
The function code specifies commands. There are three function codes, as shown below.
Function Code
(Hexadecimal)
03H
08H
10H
Data
Configure consecutive data by combining the storage register address (test code for a loopback address) and
the data the register contains. The data length changes depending on the command details.
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Data
Error check
PLC to Inverter
Command message
Response message
24 bits long
H5-06
setting
Fig 6.56 Message Spacing
Function
Read storage register contents
Loopback test
Write multiple storage registers
Inverter to PLC
PLC to Inverter
Command message
24 bits long
5 ms min.
Command Message
Min.
(Bytes)
8
8
11
Time (Seconds)
Response Message
Max.
Min.
Max.
(Bytes)
(Bytes)
(Bytes)
8
7
37
8
8
8
41
8
8
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Troubleshooting
