Signal loss detection (Pr. 122)
If a signal loss (communication stop) is detected between the inverter and master as a result of
a signal loss detection, a communication fault (E.PUE) occurs and the inverter trips (as set in
When the setting is "9999", communication check (signal loss detection) is not made.
When the setting value is "0" (initial value), RS-485 communication can be made. However, a
communication fault (E.PUE) occurrs as soon as the inverter is switched to the operation mode
(network operation mode in the initial setting) with the control.
A signal loss detection is made when the setting is any of "0.1s to 999.8s". To make a signal loss
detection, it is necessary to send data (refer to Mitsubishi inverter protcol control code (page
6-237), Modbus-RTU comunciation protocol (page 6-253)) from the computer within the com-
munication check time interval. (The inverter makes communication check (clearing of com-
munication check counter) regardless of the station number setting of the data sent from the
Communication check is made from the first communication in the operation mode with control
source valid (network operation mode in the initial setting).
PU connector communication, Pr. 122 = 0.1–999.8s
⇓ Data flow
⇓ Data flow
Fig. 6-117: Signal loss detection
Always set the communication check time interval before starting operation to prevent haz-
Data communication is not started automatically but is made only once when the computer
provides a communication request. If communication is disabled during operation due to sig-
nal cable breakage etc., the inverter cannot be stopped. When the communication check
time interval has elapsed, the inverter will come to an alarm stop (E.PUE). The inverter can
be coasted to a stop by switching on its RES signal or by switching power off.
If communication is broken due to signal cable breakage, computer fault etc., the inverter
does not detect such a fault. This should be fully noted.
Communication operation and setting
6 - 229