4. Modbus RTU
4 - 8
The following shows the information in each Response Message.
Message
Description
Slave Address
The station number "02h" is returned.
Function
The value "03h" is returned. This means that the message was received without errors.
Byte Count
The value "08h" is returned. This means that data of 8 frames is returned.
Data
Data starting from the start address is returned.
Lower-bit value of the register 2B05h: "5678h"
Higher-bit value of the register 2B05h: "1234h"
Value of the register 2B06h: "1000h"
Value of the register 2B07h: "2000h"
The endian setting of 4-byte data can be selected with "Modbus RTU communication endian
selection” of [Pr. PC72 Function selection C-G]. This example shows the case when the standard
endian (initial value) is set.
CRC Check
Data for CRC error check
This data is calculated automatically by a servo amplifier, and the result of the calculation is
returned.
4.8.3 Diagnostics (Function diagnostics: 08h)
Use this register when performing the communication check from the master (controller). When a slave
(servo amplifier) received a Query Message, the slave sends the received data as a Response Message
without any changes to the master (controller).
(1) Message frame
Query Message
Slave Address
Function
Sub Function
Data
CRC Check
H
L
H
L
L
H
(8 bits)
08h
00h
00h
(8 bits)
(8 bits)
(8 bits)
(8 bits)
Message
Size
Description
Slave Address
8 bits
Set a station number to which the message is sent.
The number "0" (station number for broadcast sending) cannot be set.
Function
8 bits
Set "08h".
Sub Function
16 bits
Set "0000h".
When a value other than "0000h" is set, a communication error occurs.
Data
16 bits
Set 2-byte length data.
CRC Check
16 bits
Data for CRC error check
This data is calculated automatically by a controller.
Response Message
Slave Address
Function
Sub Function
Data
CRC Check
H
L
H
L
L
H
(8 bits)
08h
00h
00h
(8 bits)
(8 bits)
(8 bits)
(8 bits)
Message
Size
Description
Slave Address
8 bits
The station number of a slave (servo amplifier) is returned.
Function
8 bits
When the Query Message was received without errors, "08h" is returned.
Sub Function
16 bits
The value "0000h" is returned.
Data
16 bits
The data set in the Query Message is returned.
CRC Check
16 bits
Data for CRC error check
This data is calculated automatically by a servo amplifier, and the result of the
calculation is returned.
Содержание MR-JE-C Series
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