Mitsubishi Electric 800 Series Instruction Manual page 154

 Alarm (LF) signal output (communication error warning)
• During a communication error, the Alarm (LF) signal is output by open collector output. Assign the terminal to be used using
any of Pr.190 to Pr.196 (Output terminal function selection).
Master
Alarm data
Slave
Communication
0
error count
(Pr.343)
OFF
Signal LF
NOTE
• The LF signal can be assigned to an output terminal by setting Pr.190 to Pr.196. Changing the terminal assignment may affect
other functions. Set parameters after confirming the function of each terminal.
 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 from the computer within the communication check time 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
Computer
Inverter
Pr.122
Communication
check counter
ALM
NOTE
• The operation at a communication error occurrence depends on the setting of Pr.502 Stop mode selection at
communication error. (Refer to
Alarm data Normal data
Not increased
ON
Communication error count is increased in
synchronization with leading edge of LF signal
External
PU
Check start
OFF
page 160.)
Alarm data
Reply data
1
OFF
Turns off when normal data is received
Alarm data : Data resulting in
communication error.
Fault (E.PUE)
Normal data
Reply data
2
OFF
ON
Time
ON
3. RS-485 Communication
3.5 MODBUS RTU
1
2
3
4
5
6
7
8
9
10
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