Modbus-Rtu Communication Specifications (Pr. 331, Pr. 332, Pr. 334, Pr. 343, Pr. 539, Pr. 549) - Mitsubishi Electric FR-A720-0.4K Instruction Manual

4.24.6 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 communication station
331
number
332 RS-485 communication speed
RS-485 communication parity
334
check selection
343 Communication error count
Modbus-RTU communication
539
check time interval
549 Protocol selection
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 (initial value 0).
Some functions are invalid for broadcast communication. (Refer to page 349)
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 322)
(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
1 to 247
3, 6, 12, 24, 48,
96
96, 192, 384
2
0
9999
0.1 to 999.8s
0
Description
Modbus-RTU protocol
EIA-485 (RS-485)
1: N (maximum 32 units), setting is 0 to 247 stations
Selected among 300/600/1200/2400/4800/9600/19200/38400bps
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
Not used
Not used
Communication operation and setting
Description
0 Broadcast communication is selected.
Specify 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
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
Modbus-RTU communication can be
0 made, but the inverter trips in the NET
operation mode.
Set the interval of communication check time.
(same specifications as Pr. 122)
No communication check (signal loss
9999
detection)
Mitsubishi inverter (computer link)
0
protocol
1 Modbus-RTU protocol
1bit
Related
4
Parameters
Pr. 549
⎯
Pr. 331
Pr. 332
⎯
⎯
⎯
⎯
Pr. 334
⎯
⎯
⎯
347