Mitsubishi Electric 800 Series Instruction Manual page 125

 Keepalive time (Pr.1455)
An alive check message (KeepAlive ACK) is sent to a device if the device does not return any response within the time set in
Pr.1455 Keepalive time while a TCP connection is established. When no response is returned after the seventh transmission,
the connection will be forced to be closed.
Inverter
Time set
in Pr.1455
Time set
in Pr.1455
Time set
in Pr.1455
Time set
in Pr.1455
Timeout
Time
(connection close)
124
2. Ethernet Communication
2.14 Ethernet communication parameters
Connected device
Normal communication
KeepAlive ACK (first)
KeepAlive ACK (second)
KeepAlive ACK (seventh)
No response
No response
No response