Precautions - Mitsubishi Electric Q03UDVCPU User Manual

3.6

Precautions

(1) IP address duplication
Check that the IP address is not duplicated when configuring a network or connecting a new device to a network.
If the IP address is duplicated, a device may communicate with the wrong device.
Check for the IP address duplication in the following ways.
• Check for the IP address duplication with the find CPU function.
• Disconnect the device from the line and send ping to the IP address of the disconnected device.
Having a response means the IP address duplication.
(2) KeepAlive check
When the protocol is set to TCP, KeepAlive check is performed. (Checking for a response to a KeepAlive ACK
message)
An alive check message is sent five seconds after reception of the last message from the connected device to
check if the device returns a response or not. If no response is received, the alive check message will be resent
at intervals of five seconds. When no response is received for 45 seconds, the connected device is regarded as
non-existent and the connection is disconnected. If the connected device does not support the TCP KeepAlive
function, the connection may be disconnected.
(3) Connections exceeding the setting
Do not exceed the number of connections set for the Ethernet configuration or the open settings parameters.
Establishing too many TCP connections from a personal computer may cause the following states, depending on
the application.
• Time before timeout error detection is increased.
• An unexpected timeout error occurs in any of the communicating devices.
(4) Retransmission on TCP connection
If no ACK response is returned from the other end of a TCP connection, the ACK will be resent six times, starting
in 0.3 seconds after the first transmission, and then 0.6, 1.2, 2.4, 4.8, and 9.6 seconds. When no TCP ACK
response is returned within 19.2 seconds after the last retransmission, the device is regarded as faulty and the
connection is disconnected. (As a result, the connection is disconnected in total of 38.1 seconds.)
CHAPTER 3 CONNECTION OF PROGRAMMING TOOLS AND GOT
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