4. Modbus RTU
4 - 7
Response Message
Slave Address
Function
Byte Count
Data
CRC Check
H
L
to
H
L
L
H
(8 bits)
(8 bits)
(8 bits)
(8 bits)
(8 bits)
to
(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 message was received without errors, "03h" is returned.
Byte Count
8 bits
The Data frame size (in units of bytes) is returned.
A value obtained by multiplying the value set for No. of Points in the Query
Message by 2 is returned.
Data (Note)
16 bits × n
Data starting from the start address specified in the Query Message is returned.
Data is read in order of H (higher bits) and L (lower bits).
Data is read in order starting from the start address.
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.
Note. Higher 8 bits of 1-byte data are set to "00h" when this data is returned. To use the signed 1-byte data as 2-byte data, perform sign
extension on the master (controller) side.
(2) Usage example
The following shows a setting example of when Modbus registers 2B05h (Command pulse frequency) to
2B07h (Analog torque limit voltage) in the slave address "02" are read.
Index
Name
Data type
Access
No. of Points
Continuous
read/write
Register value
(Read data)
2B05h
Command pulse frequency
I32
ro
2
12345678h
2B06h
Analog speed command voltage
I16
ro
1
1000h
2B07h
Analog torque limit voltage
Analog torque command voltage
I16
ro
1
2000h
Query Message
Slave Address
Function
Starting Address
No. of Points
CRC Check
H
L
H
L
L
H
02h
03h
2Bh
05h
00h
04h
(8 bits)
(8 bits)
Set the following values to each Query Message.
Message
Description
Slave Address
Set the station number "02h".
Function
Set "03h".
Starting Address
Set "2B05h", the start address to read.
No. of Points
Set "04h", because the total number of read points from Modbus registers 2B05h to 2B07h is 4.
CRC Check
Data for CRC error check
This data is calculated automatically by a controller.
Response Message
Slave Address
Function
Byte Count
Data
CRC Check
H
L
H
L
H
L
H
L
L
H
02h
03h
08h
56h
78h
12h
34h
10h
00h
20h
00h
(8 bits)
(8 bits)
Содержание MR-JE-C Series
Страница 9: ...A 8 MEMO ...
Страница 13: ...4 MEMO ...
Страница 33: ...2 CC Link IE Field Network Basic SLMP 2 16 MEMO ...
Страница 73: ...5 PARAMETERS 5 14 MEMO ...
Страница 79: ...6 MANUFACTURER FUNCTIONS 6 6 MEMO ...
Страница 143: ...MEMO ...