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11
TROUBLESHOOTING
No.
Symptom
6
Communication
with target device
cannot be made
even though each
parameter setting
is completed.
11 - 9
Check Item
Check the local station IP address
(intelligent function module switch 3, 4)
setting.
Check the intelligent function module
switch 2 (communication condition
setting) -b3: Send frame specification
selection.
Check the network cable connection.
Check the network cable specifications. Confirm the specifications of the used
Check whether data has reached the
target device.
Check the target device.
• Check for errors.
• Check whether the target device is
ready for operation.
• Check whether the target device is
attempting to communicate with the
QJ71MT91.
Check the line status.
Check for any TCP connection
disconnected automatically by the
KeepAlive function.
When the QJ71MT91 is the master,
check if the communication target device
is a MODBUS/TCP slave device.
When the QJ71MT91 is a slave, check if
the communication target device is a
MODBUS/TCP master device.
Check if the number of TCP connections
connected simultaneously is within 64.
Corrective Action
If necessary, correct the setting and
reset the CPU.
If necessary, correct the setting and
reset the CPU.
Connect the network cable correctly.
network cable.
• Conduct a PING test to check the
target device status and line status.
If the data has not reached the target
device, check the route and line status,
and take corrective action if necessary.
• When data is sent via a router, check
the routing information settings of the
QJ71MT91 and target device.
Take corrective action if the target
device has any problem.
Correct the line status if it has any
problem in traffic.
• Check that the target device is
operating normally.
• Adjust the KeepAlive start timer value
and KeepAlive interval timer value.
Set a MODBUS/TCP slave device as
the communication target.
Set a MODBUS/TCP master device as
the communication target device.
• Retry as TCP connections may fail
temporarily.
• TCP connections with the nodes not
specified as preferred ones may be
disconnected automatically when the
connection resources become
insufficient. Specify the nodes as
preferred ones when necessary.
• Reduce the number of simultaneously
connected connections.
MELSEC-Q
Reference
Section
Section 6.6
Section 6.6
Section 6.4
Section 3.1
Section 7.2
Section 11.5
Section 5.4
Section 7.2
Section 3.1
Section 7.2
11 - 9
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