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Mitsubishi Electric FR-F740-00023 Instruction Manual: Modbus-rtu Communication Specifications

F700 series.
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4.19.6 Modbus-RTU communication specifications

(Pr. 331, Pr. 332, Pr. 334, Pr. 343, Pr. 539, 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
331
communication
station number
RS-485
332
communication
speed
RS-485
334
communication parity
check selection
Communication error
343
count
Modbus-RTU
539
communication check
time interval
549
Protocol selection
The above parameters can be set when Pr. 160 User group read selection = "0". (Refer to page 173)
CAUTION
When Modbus-RTU communication is performed from the master with address 0 (station 0) set, 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 209.)
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 184)
(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
Setting Range
Value
0
0
1 to 247
3, 6, 12, 24, 48,
96
96, 192, 384
0
2
1
2
0
0
9999
0.1 to 999.8s
9999
0
0
1
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
Description
Broadcast communication is selected.
Specifies the inverter station number.
Set the inverter station numbers when two or more
inverters are connected to one personal computer.
Set the communication speed.
The setting value
100 equals the communication speed.
For example, the communication speed is 9600bps when
the setting value is "96".
Without parity check
Stop bit length 2bits
With odd parity check
Stop bit length 1bit
With even parity check
Stop bit length 1bit
Displays the number of communication errors during
Modbus-RTU communication. Reading only
Modbus-RTU communication can be made, but the inverter
will come to trip in the NET operation mode.
Set the interval of communication check time.
(same specifications as Pr. 122)
No communication check (signal loss detection)
Mitsubishi inverter (computer link) protocol
Modbus-RTU protocol
Description
1bit
Not used
Not used
Related
Parameters
4
Pr. 549
Pr. 331
Pr. 332
Pr. 334
207

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