Mitsubishi Electric FR-F820-00046 Instruction Manual page 511

• 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"
Query communication
Operation mode
Communication
check counter
Broadcast communication
Operation mode
Communication
check counter
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
510
5. PARAMETERS
5.12 (N) Communication operation parameters
External
PLC (master)
Inverter (slave)
Inverter (slave)
PLC (master)
Pr.539
ALM
External
Query Message1
PLC (master)
Inverter (slave)
Inverter (slave)
PLC (master)
Pr.539
ALM
NET
Query Message1 Query Message2
Data absence time
(3.5 bytes or more)
Response Message1
Check start
OFF
NET
Query Message2
Data absence time
(3.5 bytes or more)
Check start
OFF
page 478.)
Fault
(E.SER)
Response Message2
Time
ON
Fault
(E.SER)
Time
ON