Signal Loss Detection (Pr.539 Modbus Rtu Communication Check Time Interval) - Mitsubishi Electric 800 Series Instruction Manual

4.5.15

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 Communication 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.
Example: Pr.539 = "0.1 to 999.8 s"
Query communication
Operation mode
PLC (master)
Inverter (slave)
Inverter (slave)
PLC (master)
Communication
check counter
86
PARAMETER
External NET
Query Message1
Pr.539
ALM
Query Message2
Data absence time
(3.5 bytes or more)
Response Message1 Response Message2
Check start
OFF
Fault
(E.SER)
Time
ON