Mitsubishi PLC and Mitsubishi inverter ModbusRTU protocol communication application - Database & Sql Blog Articles

Probe high frequency needle JTK-50L-Q has 5 needles in the high frequency needle

Crystal oscillator 2.5*2.0mm 2520 0.67M~170M OSC can be supplied at any frequency

Photocoupler

Modbus is a serial communication protocol invented for communication between its plc and the host. The physical layer uses asynchronous serial standards such as RS232 and 485. Due to its openness, it has been adopted by a large number of PLC and RTU manufacturers. The Modbus communication mode adopts the master-slave mode query-corresponding mechanism. Only when the master station issues a query, the slave station can give a response, and the slave station cannot actively send data. The primary station can issue a query to one of the secondary stations or broadcast information to all secondary stations. The slave only responds to queries sent to it separately, and does not respond to broadcast messages. The MODBUS communication protocol has two transmission modes: RTU mode and ASCII mode. The Mitsubishi 700 series inverter can use the ModbusRTU communication protocol from the RS-485 terminal for communication operation and parameter setting.

Object:

1. Mitsubishi plc: FX2N+FX2N-485-BD

2. Mitsubishi inverter: F700 series, A700 series.

The two are connected by a network cable, as shown in the following figure.

Connection diagram of FX2N-485-BD and n inverters

When communication between the PLC and the inverter, the communication specifications must be set in the inverter. After each parameter initialization setting, the inverter needs to be reset or the inverter power supply is turned on and off.

Parameter number name setting value description

Pr331 Communication station number 1 Set the inverter station number to 1

Pr332 communication speed 96 sets the communication speed to 9600bps

Pr334 parity stop bit length 2 even parity, stop bit length 1 bit

Pr539 communication check time 9999 does not perform communication check

Pr549 protocol selection 1 ModbusRTU protocol

Pr551 PU mode operation right selection 2 PU operation mode operation right as PU interface

When communicating with ModbusRTU protocol, Pr551 must be set to 2, Pr340 is set to a value other than 0, and Pr79 is set to 0 or 2 or 6. When communicating via the RS-485 terminal for ModbusRTU protocol, it must be run in NET network mode.

Set the communication format D8120

The D8120 setting value is 0C87, that is, the data length is 8 bits, the even parity stop bit is 1 bit, the baud rate is 9600pbs, ​​and there is no title character and terminator.

After modifying the D8120 settings, make sure that the PLC power is turned on and off once.

Four: program description:

1. When X1 is turned on once, the inverter enters the forward rotation state.

2. When X2 is turned on once, write the inverter running frequency 60HZ.

3. When X3 is turned on once, the inverter enters the stop state.

When the command address of the inverter is 0, it is a broadcast command. All slave inverters only accept commands from the PLC and do not send response messages to the host.