Modbus Rtu 4- 1 To; Outline; Communication Specifications - Mitsubishi Electric MR-JE-C Series Instruction Manual

4. Modbus RTU
4. Modbus RTU

4.1 Outline

The Modbus protocol developed for programmable controllers is provided by Modicon Inc.
The Modbus protocol uses dedicated message frames for the serial communication between a master and
slaves. Using the functions in the message frames enables to read or write data from/to parameters, write
input commands, and check operation status of servo amplifiers.
For MR-JE-_C servo amplifier, Modbus registers are assigned like the address assignment of CiA 402 drive
profile.
A Modbus-compatible controller, the master, can communicate with the MR-JE-_C servo amplifiers that are
slaves by accessing assigned holding registers.
The ASCII (American Standard Code for Information Interchange) mode and the RTU (Remote Terminal
Unit) mode are provided as the serial transmission modes of the Modbus protocol. The MR-JE-_C servo
amplifiers support only the RTU mode.

4.2 Communication Specifications

Item
Communication protocol
Conformed standard
Number of connectable modules
Communication baud rate [bps]
Control procedure
Communication method
Character method
Start bit
Stop bit length
Communication
specifications
Parity check
Error check
Terminator
Waiting time setting
Master/slave type
POINT
Modbus RTU is available with servo amplifiers with software version A4 or later.
RS-485 communication (Modbus RTU) and Ethernet communication function
are mutually exclusive. They cannot be used together. In addition, MR
Configurator2 cannot be used with an Ethernet port. Connect a servo amplifier
to MR Configurator2 with a USB port.
Modbus RTU protocol
EIA-485 (RS-485)
1: n (up to 32 modules), Setting: Station 1 to station
247 (Station 0: Station number for the broadcast
communication)
Up to 32 modules including other slave devices
such as inverters can be connected.
4800/9600/19200/38400/57600/115200
Asynchronous serial communication
Half duplex
Binary (fixed to 8 bits)
1 bit
Select from the following three types.
Even parity, stop bit length of 1 bit (Initial setting)
Odd parity, stop bit length of 1 bit
No parity, stop bit length of 2 bits
CRC-16 method
None
None
Slave
Description
4 - 1
Remark
Select "RS-485 communication" with
"communication function selection"
of [Pr. PN08 Function selection N-2].
Set the station numbers with [Pr.
PC70 Modbus RTU communication
station number setting].
Select with "Modbus RTU
communication baud rate selection"
of [Pr. PC71 Function selection C-F].
Select with "Protocol parity selection"
of [Pr. PF45 Function selection F-
12].