Modbus is a serial communication protocol invented by Modicon for communication between PLCs and hosts. Its physical layer uses asynchronous serial standards such as RS232 and RS485. Due to its openness, it has been adopted by numerous PLC and RTU manufacturers.
The Modbus communication method adopts a master-slave query-response mechanism, where only the master can issue queries and the slave can respond; the slave cannot actively send data. The master can issue queries to a specific slave or broadcast information to all slaves. The slave only responds to queries sent specifically to it and does not respond to broadcast messages. There are two transmission modes in the MODBUS communication protocol: RTU mode and ASCII mode.
The Mitsubishi 700 series inverter can communicate using the Modbus RTU protocol from the RS-485 terminal for operational communication and parameter setting.
Objects:
1. Mitsubishi PLC: FX2N + FX2N-485-BD
2. Mitsubishi Inverters: F700 series, A700 series.
They are connected via a network cable, refer to the diagram below.
Connection diagram of FX2N-485-BD and multiple inverters
Settings for Mitsubishi Inverter
When communicating between the PLC and the inverter, the communication specifications must be set in the inverter. After each parameter initialization, the inverter must be reset or power cycled.
Parameter Number Name Setting Value Description
Pr331 Communication Station Number 1 Set the inverter station number to 1
Pr332 Communication Speed 96 Set the communication speed to 9600 bps
Pr334 Parity Stop Bit Length 2 Even parity, stop bit length 1
Pr539 Communication Check Time 9999 No communication check
Pr549 Protocol Selection 1 Modbus RTU protocol
Pr551 PU Mode Operation Rights Selection 2 PU operation mode rights as PU interface
When communicating using the Modbus RTU protocol, Pr551 must be set to 2, Pr340 set to a value other than 0, and Pr79 set to 0, 2, or 6. When communicating via the RS-485 terminal using the Modbus RTU protocol, it must operate in NET network mode.
Settings for Mitsubishi PLC
Set the communication format D8120
The setting value for D8120 is 0C87, which means data length is 8 bits, even parity, stop bit 1, baud rate 9600 bps, no header and footer.
After modifying the D8120 setting, ensure to power cycle the PLC once.
Communication Program
Part of the PLC program for communicating with the inverter using Modbus RTU protocol is as follows:
Program Description
1. When X1 is activated once, the inverter enters the forward rotation state.
2. When X2 is activated once, the running frequency of the inverter is set to 60HZ.
3. When X3 is activated once, the inverter enters the stop state.
When in the command, if the inverter command address is 0, it is a broadcast command; all slave inverters only accept commands issued by the PLC and do not send response information to the host.
The editor has compiled 1117 examples of Mitsubishi PLC project practical cases, including classic project applications from various industries, friends who are interested can scan the code to receive it for free!
1117 Mitsubishi PLC Cases
Long press the QR code to receive it immediately
Disclaimer: This article is reproduced from the internet, and the copyright belongs to the original author. If there are any copyright issues, please contact us in time for deletion, thank you!
Complete question bank for the 2022 Electrician Junior Exam (including answers)
3 essential tools for electricians, easily accessible via WeChat!
[Collection] “Path” for ten-year veteran electricians, secrets to earning over ten thousand a month!
Which of the five major electrical drawing software (CAD, Eplan, CADe_simu…) do you pick?
The latest electrical CAD drawing software, with a super detailed installation tutorial!
The latest electrical drawing software EPLAN, with a super detailed installation tutorial!
Common issues for beginners using S7-200 SMART programming software (with download links)
Comprehensive electrical calculation EXCEL sheets, automatically generated! No need to ask for electrical calculations!
Bluetooth headsets, introductory books on electricians/PLC, freely given? Come and claim your electrical gifts!
Basic skills in PLC programming: Ladder diagrams and control circuits (with 1164 practical cases of Mitsubishi PLC)
Still can’t understand electrical diagrams? Basic skills for electricians, simulation software to get started quickly!
12 free electrician video courses, 10GB software/e-book materials, and 30 days of free electrician live classes are being given away!
