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11
TROUBLESHOOTING
Error
Error Name
Code
7452
H
Connection
not open
7453
H
Connection
7454
H
being closed
TCP receive
7455
H
data size error
TCP ULP
7460
H
timeout error
TCP
connection
7461
H
forcibly
disconnected
TCP
connection
7462
H
forcibly
disconnected
TCP protocol
7463
H
error
UDP receive
7471
H
data size error
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Description
• Transmission was
attempted using the
connection not open.
• The connection used to
send data was already
closed.
The connection being closed
was used to send data.
The connection not open was
used to send data.
The message greater than
the TCP maximum size was
received.
As the TCP ULP timer timed
out, the TCP connection was
forcibly disconnected from
the local station.
The TCP connection was
disconnected forcibly from
the target device.
(This error may be ignored
when no problems arise from
this error.)
• The TCP connection was
closed forcibly from the
local station.
• The local station uses 64 or
more TCP connections.
Hence, the TCP connection
was closed forcibly to
maintain the TCP
connections available for
simultaneous opening
under frequently opened
and closed conditions. (This
error may be ignored when
no problems arise from this
error.)
As a TCP protocol error was
detected, the TCP
connection was closed
forcibly.
The message greater than
the UDP maximum size was
received.
Lit LED
Corrective Action
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
COM.ERR.
error.
• Retry after a little while.
Retry after a little while.
Retry after a little while.
COM.ERR.
• Check whether the operation
status of the target device is
normal or not.
COM.ERR.
• Check the line status for an
error.
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
error.
COM.ERR.
• As the line may be busy, retry
after a little while.
• Review the TCP ULP timer
value of the basic parameter.
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
COM.ERR.
error.
• As the line may be busy, retry
after a little while.
• In the preferred node
specification, specify the
target device with which
communication is made
frequently.
• Decrease the number of TCP
connections used
simultaneously.
COM.ERR.
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
error.
• As the line may be busy, retry
after a little while.
• Check whether the operation
status of the target device is
normal or not.
COM.ERR.
• Check the line status for an
error.
• Check whether the operation
status of the target device is
normal or not.
COM.ERR.
• Check the line status for an
error.
MELSEC-Q
Occurrence
1)
2)
3)
4)
5)
(Continued on next page)
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