Modbus-Rtu Communication Specifications (Pr. 331, Pr. 332, Pr. 334, Pr. 343, Pr. 549) - Mitsubishi Electric FR-F740-00023-EC Instruction Manual

3.18.6 Modbus-RTU communication specifications (Pr. 331, Pr. 332, Pr. 334, Pr. 343, Pr. 549)

Using the Modbus-RTU communication protocol, communication operation or parameter setting can be
performed from the RS-485 terminals of the inverter.
Parameter
Name
Number
RS-485 communication station
331
number
332 RS-485 communication speed
RS-485 communication parity
334
check selection
343 Communication error count
549 Protocol selection
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 146)
CAUTION
When ModbusRTU communication is performed with "0" (initial value) set in Pr. 331 RS-485 communication station number,
broadcast communication is selected and the inverter does not send a response message to the master.
When response from the inverter is necessary, set a value other than "0" in Pr. 331.
Some functions are invalid for broadcast communication. (Refer to page 181.)
REMARKS
⋅ When using the Modbus-RTU protocol, set Pr. 549 Protocol selection to "1".
⋅ When the communication option is fitted with Pr. 550 NET mode operation command source selection set to "9999" (initial value), the
command source (e.g. run command) from the RS-485 terminals is invalid. (Refer to page 157)
(1) Communication specifications
⋅ The communication specifications are given below.
Item
Communication protocol
Conforming standard
Number of inverters connected
Communication speed
Control protocol
Communication method
Character system
Start bit
Stop bit length
Communication
specifications
Parity check
Error check
Terminator
Waiting time setting
Initial Value Setting Range
0
3, 6, 12, 24, 48,
96
2
0
0
Modbus-RTU protocol
EIA-485 (RS-485)
1: N (maximum 32 units), setting is 0 to 247 stations
Can be selected from 300, 600, 1200, 2400, 4800, 9600, 19200 and 38400bps
Asynchronous system
Half-duplex system
Binary(fixed to 8 bits)
Select from the following three types
⋅ No parity, stop bit length 2 bits
⋅ Odd parity, stop bit length 1 bit
⋅ Even parity, stop bit length 1 bit
CRC code check
Communication operation and setting
0 Broadcast communication is selected.
Specify the inverter station number.
Set the inverter station numbers when two
1 to 247
or more inverters are connected to one
personal computer.
Set the communication speed.
The setting value × 100 equals the
communication speed.
96, 192, 384
For example, the communication speed is
9600bps when the setting value is "96".
Without parity check
0
Stop bit length 2bits
With odd parity check
1
Stop bit length 1bit
With even parity check
2
Stop bit length 1bit
Display the number of communication

errors during Modbus-RTU
communication. Reading only
0 Mitsubishi inverter (computer link) protocol
1 Modbus-RTU protocol
Description
1bit
Not used
Not used
Description
Related
Parameters
Pr. 549

Pr. 331
Pr. 332




Pr. 334



179
Pr.299
page 114
Pr.333
page 167
Pr.335
page 167
Pr.342
page 168
Pr.495
page 103
Pr.504
page 219
Pr.550
page 157
3