Mitsubishi Electric 800 Series Instruction Manual page 137

NOTE
• The operation at a communication error occurrence depends on the setting of Pr.502 Stop mode selection at
communication error. (Refer to
 Signal loss detection (Pr.122)
• If a signal loss (communication stop) is detected between the inverter and computer as a result of a signal loss detection,
a communication error (E.PUE) occurs and the inverter output will be shut off.
• When a signal loss is detected, the LF signal is output.
• When the setting is "9999", communication check (signal loss detection) is not made.
• When the setting is "0", communication through the PU connector is not possible.
• A signal loss detection is made when the setting is any of "0.1 s to 999.8 s". To make a signal loss detection, it is necessary
to send data (for details on control codes, refer to
interval. (The inverter makes a communication check (clearing of communication check counter) regardless of the station
number setting of the data sent from the master). Communication check is started at the initial communication in the
operation mode for the selected command interface (PU operation mode for PU connector communication in the initial
setting).
Example: PU connector communication, Pr. 122 = "0.1 to 999.8s"
Operation Mode
Computer
Inverter
Inverter Computer
Communication
check counter
ALM
 Programming instructions
• When data from the computer has any error, the inverter does not accept that data. Hence, in the user program, always
insert a retry program for data error.
• All data communication, for example, run command or monitoring, are started when the computer gives a communication
request. The inverter does not return any data without the computer's request. Hence, design the program so that the
computer gives a data read request for monitoring, etc. as required.
CAUTION
• Always set the communication check time interval before starting operation to prevent hazardous conditions.
• 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 signal cable breakage etc., the inverter cannot be stopped.
When the communication check time interval has elapsed, the inverter output will be shut off (E.PUE). Turn the RES
signal of the inverter ON or shut off the power supply to coast the motor to a stop.
• 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.
136
3. RS-485 Communication
3.4 Mitsubishi inverter protocol (computer link communication)
page 160.)
External
PU
Pr.122
OFF
page 133) from the computer within the communication check time
Check start
Fault (E.PUE)
Time
ON