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Communication operation and setting
4.18.6 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 drive unit.
Parameter
number
Name
Initial
value
Setting
range
Description
117
PU communication
station number
0
0 No reply to the master
1 to 247
Drive unit station number specification
Set the drive unit station numbers when two or more drive units are
connected to one personal computer.
118 PU communication speed
192
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 2 bits
1
With odd parity check
Stop bit length 1 bit
2
With even parity check
Stop bit length 1 bit
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 drive unit 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 drive unit trips (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, 3 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 182)
When Modbus-RTU communication is performed from the master with address 0 (station number 0) set, broadcast communication is selected and the drive
unit does not send a response message. When response from the drive unit 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 225)
NOTE
When "1" (Modbus-RTU protocol) is set in Pr.549 and "384" (38400bps) in Pr.118, parameter unit (FR-PU07) is disabled.
When using the parameter unit (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 command source (when Pr.550 NET mode operation command source selection = "2"
or "9999" (initial value) without communication option), Modbus-RTU communication operation can be performed. (Refer to page
195)