Mitsubishi Electric FR-A700 Instruction Manual page 665

Parameter
Signal loss detection (Pr. 539)
If a signal loss (communication stop) is detected between the inverter and master as a result of
a signal loss detection, a communication error (E.SER) occurs and the inverter output is shut off.
When the setting is "9999", communication check (signal loss detection) is not made.
When the setting value is "0", monitor, parameter read, etc. can be performed. However, a com-
munication error (E.SER) occurs as soon as the inverter is switched to the network operation
mode.
A signal loss detection is made when the setting is any of "0.1s to 999.8s". To make a signal loss
detection, it is necessary to send data from the master within the communication check time
interval. (The inverter makes communication check (clearing of communication check counter)
regardless of the station number setting of the data sent from the master.)
Communication check is started from the first communication after switching to the network ope-
ration mode (use Pr. 551 "PU mode operation command source selection" to change).
Communication check time of query communication includes data absence time (3.5 byte).
Since this data absence time differs according to the communication speed, make setting con-
sidering this absence time.
Example RS-485 terminal communication, Pr. 539 = "0.1 to 999.8s"
Fig. 6-233: Signal loss detection
FR-A700 EC
Query communication
Operation mode External
PLC (master)
⇓
Inverter (slave)
Inverter (slave)
⇓
PLC (master)
Pr. 539
Communication
check counter
Broadcast communication
Operation mode External
PLC (master)
⇓
Inverter (slave)
Inverter (slave)
⇓
PLC (master)
Pr. 539
Communication
check counter
Communication operation and setting
NET
Query Message 1
Query Message 2
Data absence time
(3.5 bytes or more)
Response Message 1
Check start
NET
Query Message 1 Query Message 2
Data absence time
(3.5 bytes or more)
Check start
Alarm (E.SER)
Response Message 2
Alarm (E.SER)
Time
Time
I001622E
6 - 485