Function Codes; List Of Function Codes; Read Holding Registers (Reading Data In Holding Registers: 03H) - Mitsubishi Electric MR-JE-C Series Instruction Manual

4. Modbus RTU

4.8 Function Codes

4.8.1 List of function codes

The MR-JE-_C servo amplifier supports the following function codes.
Code Function name
03h Read Holding Registers
08h Diagnostics
10h Preset Multiple Registers

4.8.2 Read Holding Registers (Reading data in holding registers: 03h)

Data in consecutive registers is read for the specified number of data points starting from the specified
register address.
(1) Message frame
Query Message
Slave Address Function
(8 bits) 03h
Message
Slave Address
Function
Starting Address (Note)
No. of Points
CRC Check
Note. Registers can be classified into two types: registers that can be continuously accessed and particular registers that cannot be
continuously accessed.
To read particular registers, read only the target registers.
For the details on whether the target registers can be continuously accessed or not, refer to the directions for use of each function
of the Modbus registers described in chapter 7.
Reading data in holding registers
The data in the registered holding registers can be read from the
master.
Function diagnostics
When this function code is sent from the master to a slave, the
slave returns the received data to the master without any
changes.
Communication checks can be performed.
Writing data in multiple holding registers
Continuous multiple data sets can be written in the registered
holding registers from the master.
Starting Address
H L
(8 bits) (8 bits)
Size
Set a station number to which the message is sent.
8 bits
The number "0" (station number for broadcast sending) cannot be set.
8 bits Set "03h".
16 bits Set a start address of the holding registers to read.
Set the number of points of data to read starting from the start address of the
holding registers from which data is read.
16 bits Set the number of read points described in the list of holding registers.
To read the data in continuous registers, set a value obtained by adding the
number of read points of the target registers to this number.
Data for CRC error check
16 bits
This data is calculated automatically by a controller.
4 - 6
Description
No. of Points
H L
(8 bits) (8 bits)
Description
Broadcast communication
Not supported
Not supported
Supported
CRC Check
L H
(8 bits) (8 bits)