Mitsubishi Electric FR-F800 Series Instruction Manual page 533

 Signal loss detection (Pr.539 RS-485 communication check time interval)
• If signal loss is detected between the inverter and the master, the Communication fault (inverter) (E.SER) will occur and
the inverter output will be shut off.
• 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 E.SER occurs instantly when the
operation mode is switched to the Network operation.
• Setting any value from 0.1 s to 999.8 s will enable signal loss detection. To detect signal loss, data must be sent 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 no-data time into consideration when setting
the communication check time.
Example: RS-485 terminal communication, Pr. 539 = "0.1 to 999.8 s"
NOTE
• For the RS-485 terminal communication, the operation at a communication error occurrence depends on the Pr.502 Stop
mode selection at communication error setting. (Refer to
532
5. PARAMETERS
5.12 (N) Communication operation parameters
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Query communication
Operation mode External
PLC (master)
Inverter (slave)
Inverter (slave)
PLC (master)
Pr.539
Communication
check counter
ALM
Broadcast communication
Operation mode External
PLC (master)
Inverter (slave)
Inverter (slave)
PLC (master)
Pr.539
Communication
check counter
ALM
search engine
NET
Query Message1
Data absence time
(3.5 bytes or more)
Response Message1
Check start
OFF
NET
Query Message1 Query Message2
Data absence time
(3.5 bytes or more)
Check start
OFF
page 500.)
Query Message2
Fault
(E.SER)
Response Message2
Fault
(E.SER)
Time
ON
Time
ON