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MELSEC-Q
11 TROUBLESHOOTING
No.
Symptom
Check Item
Corrective Action
Reference
Section
When accessing the programmable
controller CPU device in the slave
function, check if access to the
programmable controller CPU from the
other modules and sequence program is
too often.
Reduce the programmable controller
CPU loads.
Check for any TCP connection
disconnected automatically by the
KeepAlive function.
• Check that the target device is
operating normally.
• Adjust the KeepAlive start timer value
and KeepAlive interval timer value.
Section 5.4
Section 7.2
8 QJ71MT91
responds slowly.
Check if the number of TCP connections
connected simultaneously is within 64.
• TCP connections may fail temporarily.
Retry the connection.
• TCP connections with the nodes not
specified as preferred ones may be
closed automatically when the
connection resources become
insufficient. Reconnect and retry.
Specify the nodes as preferred ones
when necessary.
Section 7.2
9 Normal
communication is
not available after
replacement of
QJ71MT91 or
target device.
Check if the power was reapplied after
replacement of the QJ71MT91 or target
device.
Reapply the power of the QJ71MT91 or
target device.
(When the target device has the
Ethernet address of the communication
target, continued communication may be
disabled since the Ethernet address
changed due to the replacement of the
QJ71MT91.)
