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Communication operation and setting
4.19.3 Operation selection at communication error occurrence (Pr. 121, Pr. 122, Pr. 502)
(1) Retry count setting (Pr.121)
Set the permissible number of retries at data receive error occurrence. (Refer to page 192 for data receive error for retry)
When data receive errors occur consecutively and exceed the permissible number of retries set, an inverter trips (E.PUE)
and a motor stops (as set in Pr. 502).
When "9999" is set, an inverter fault is not provided even if data receive error occurs but an alarm signal (LF) is output.
For the terminal used for the LF signal output, assign the function by setting "98 (positive logic) or 198 (negative logic)" in
Pr. 190 or Pr. 192 (output terminal function selection).
You can select the inverter operation when a communication line error occurs during RS-485 communication from the
PU connector.
Parameter
Number
Name
Initial
Value
Setting
Range
Description
121
Number of PU
communication
retries
1
0 to 10
Number of retries at data receive error occurrence. If the number of
consecutive errors exceeds the permissible value, the inverter will
come to trip (depends on Pr. 502).
Valid only Mitsubishi inverter (computer link operation) protocol
9999 If a communication error occurs, the inverter will not come to trip.
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. (NET mode at initial value)
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)
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
The above parameters can be set when Pr. 160 Extended function display selection = "0". (Refer to page 162)
REMARKS
Pr. 121 is valid only when Mitsubishi inverter (computer link operation) protocol is selected. Pr. 121 is not valid when Modbus-
RTU communication protocol is selected.
Computer
Reception error
Reception error
Fault (E. PUE)
Inverter
Inverter
Computer
ENQ
ACK
NAK
NAK
Computer
LF OFF OFF
Reception error Reception error
Inverter
Inverter
Computer
ENQ
ACK
NAK
NAK
ON
Wrong
Wrong
ENQ
ACK
Normal
ENQ
Wrong
ENQ
Wrong
Example: PU connector communication, Pr. 121 = "1" (initial value)
Example: PU connector communication, Pr. 121 = "9999"