Mitsubishi Electric FR-A820-00046 Instruction Manual page 873

Parameters
Output signal LF "alarm output (communication error warning)"
During a communication error, the alarm signal (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
Communication
error count
(Pr. 343)
Signal LF
Fig. 5-326:
NOTE The LF signal can be assigned to an output terminal by setting Pr. 190 to Pr. 196. Changing the ter-
minal assignment may affect other functions. Set parameters after confirming the function of each
terminal.
Signal loss detection (Pr. 539 "Modbus® RTU communication check time interval")
● If a signal loss (communication) is detected between the inverter and the master as a result of a
signal loss detection, an inverter communication fault (E.SER) occurs and the inverter trips.
● When the setting is "9999", communication check (signal loss detection) is not made.
● When the setting is "0", reading, etc. of monitors and parameters is possible, though a Communi-
cation fault (inverter) (E.SER) occurs instantly when the Network operation mode is switched to.
● 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 master 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).
● The communication check is made from the first communication in the Network operation mode
(can be changed by Pr. 551 "PU mode operation command source selection").
● The communication check time by query communication includes a no data time (3.5 bytes).
This no data time differs according to the communication speed, so take this time no data time
into consideration when setting the communication check time.
FR-A800
Alarm data Alarm data
Slave
OFF
Communication error count is increased in
synchronization with leading edge of LF signal
Output of the LF signal
(N) Operation via communication and its settings
Normal data
Reply data
ON
Turns off when normal data is received
Alarm data Normal data
OFF ON
Alarm data:
Data resulting in communication error.
Reply data
OFF
I001229E
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