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Communication operation and setting
4.19.6 Modbus RTU communication specifications
(Pr. 117, Pr. 118, Pr. 120, Pr. 122, Pr. 343, Pr. 502, Pr. 549)
Using the Modbus RTU communication protocol, communication operation or parameter setting can be performed from
the PU connector of the inverter.
Parameter
Number
Name Initial Value
Setting
Range
Description
117
PU communication
station number
0
0 No reply to the master *
1 to 247
Inverter station number specification
Set the inverter station numbers when two or more inverters are
connected to one personal computer.
118
PU communication
speed
96
48, 96, 192,
384
Communication speed
The setting value × 100 equals the communication speed.
Example) 9600bps if 96
120
PU communication
parity check
2
0
Without parity check
Stop bit length 2bit
1
With odd parity check
Stop bit length 1bit
2
With even parity check
Stop bit length 1bit
122
PU communication
check time interval
0
0
RS-485 communication can be made. Note that a communication
fault (E.PUE) occurs as soon as the inverter is switched to the
operation mode with command source.
0.1 to
999.8s
Communication check (signal loss detection) time interval
If a no-communication state persists for longer than the permissible
time, the inverter will come to trip (depends on Pr. 502).
9999 No communication check (signal loss detection)
343
Communication error
count
0—
Displays the number of communication errors during Modbus-RTU
communication (reading only)
502
Stop mode selection
at communication
error
0
At Fault
Occurrence
Indication Fault Output
At Fault
Removal
0 Coasts to stop. E.PUE Output
Stop
(E.PUE)
1
Decelerates to
stop
After stop
E.PUE
Output after
stop
Stop
(E.PUE)
2
Decelerates to
stop
After stop
E.PUE
Without output
Automatic
restart functions
549 Protocol selection
0
0 Mitsubishi inverter (computer link operation) protocol
1 Modbus-RTU protocol
The above parameters can be set when Pr. 160 Extended function display selection = "0". (Refer to page 162)
* When Modbus-RTU communication is performed from the master with address 0 (station number 0) set, broadcast communication is selected and the
inverter does not send a response message. When response from the inverter is necessary, set a value other than "0" (initial value is 0) in Pr. 117 PU
communication station number.
Some functions are invalid for broadcast communication. (Refer to page 203 )
NOTE
When "1" (Modbus-RTU protocol) is set in Pr. 549 and "384" (38400bps) in Pr. 118, parameter unit (FR-PU04/FR-PU07)
is disabled. When using the parameter unit (FR-PU04/FR-PU07), change parameter using the operation panel.
REMARKS
Set Pr. 549 Protocol selection to "1" to use the Modbus RTU protocol.
When PU connector is selected as NET mode operation source (when Pr. 551 PU mode operation command source selection ≠"2"),
Modbus RTU communication operation can be performed. (Refer to page 176)