11 - 8 11 - 8
MELSEC-Q
11 TROUBLESHOOTING
No.
Symptom
Check Item
Corrective Action
Reference
Section
6 Communication
with target device
cannot be made
even though each
parameter setting
is completed.
Check if the total number of TCP
connections specified for use with
preferred nodes is within 64.
As the connection resources are all
assigned to the preferred nodes, the
other nodes cannot communicate.
Delete the unnecessary preferred node
specifications.
Section 7.2
Check the target device.
• Check for errors.
• Check whether the target device is
ready for operation.
Take corrective action if the target
device has any problem.
Check the line status.
Correct the line status if it has any
problem in traffic.
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
Check if the number of TCP connections
connected simultaneously is within 64.
• Retry as TCP connections may fail
temporarily.
• TCP connections with the nodes not
specified as preferred ones may be
closed automatically when the
connection resources become
insufficient. Specify the nodes as
preferred ones when necessary.
• Reduce the number of simultaneously
connected connections.
Section 3.1
Section 7.2
Check whether the QJ71MT91 has
issued two or more send requests
concurrently.
If two or more send requests are issued,
long time is required as they are
processed in due order. Reduce the
QJ71MT91 loads.
7 Communication
interval time with
the slave by the
automatic
communication
function is longer
than time set to
the repeat interval
timer.
Dedicated
instruction requires
a long time to be
completed.
Check whether the target device
requires a long time to respond.
• Confirm the processing performance
of the target device.
• If the target device has any problem,
check and take corrective action.
Check the specifications using the
processing time performance expression
of the QJ71MT91 slave function.
Reduce the processing time to within the
range of the performance expression.
Appendix 2
Check whether the QJ71MT91 has
issued two or more send requests
concurrently.
If two or more send requests are issued,
long time is required as they are
processed in due order. Reduce the
QJ71MT91 loads.
8 QJ71MT91
responds slowly.
Check the line status.
Correct the line status if it has any
problem in traffic.
