Mitsubishi Electric NZ2GF-ETB, User Manual

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CHAPTER 3 SPECIFICATIONS
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(4) Communication specifications for TCP connection
(a) Number of resends and resend interval
If the Ethernet adapter module sent a message to an external device and after that did not receive an ACK
from the external device, it will resend the message at the intervals shown below.
If the Ethernet adapter module fails to receive an ACK response from the external device even when it resends
data as many times as the number of resends, it regards that there is no external device, causing
disconnection.
When the connection is disconnected, send a connection establishment request from the external device,
reestablish a connection, and resend a request message.
(b) Alive check by KeepAlive
The Ethernet adapter module performs alive check by KeepAlive.
The Ethernet adapter module sends an alive check message in 5 seconds after receiving the last message
from an external device. If no response is returned from the external device for 5 seconds, the module resends
the alive check message. The module resends the message for 7 times at intervals of 5 seconds.
If no response is received for 45 seconds from the last message reception from the external device, the
Ethernet adapter module will close the connection. Allow 45 seconds or longer before opening the same
connection again.
When the external device does not support the TCP KeepAlive function, the connection may be closed.
(c) Connection establishment request
When a connection establishment request is sent from an external device to the port of the Ethernet adapter
module, where a connection has been already established, the Ethernet adapter module will not respond.
Therefore, if no response is returned even after a connection establishment request is sent to the Ethernet
adapter module, check if the specified port number is correct.
Item Specification
Number of resends Up to 3 times
Resend interval
Up to 64 seconds (Varies depending on the line status.)
If the resend fails, the amount of time is doubled. (The maximum value is 64
seconds.)
When the interval for the first resend is 20 seconds;
1st: 20s, 2nd: 40s, 3rd: 64s
Ex.