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MELSEC-Q
11 TROUBLESHOOTING
Occurrence
Error
Code
Error Name
Description
Lit LED
Corrective Action
1) 2) 3) 4) 5)
73D6
H
Send/receive
processing
interruption
The send/receive processing
was forcibly interrupted by the
basic parameter setting
processing.
COM.ERR.
Perform the basic parameter
setting processing after the
send/receive processing is over.
73D7
H
Error during
close
processing
Transmission through the
connection being closed was
attempted.
COM.ERR.
• Retry after a little while.
• If this error occurs at execution
of the dedicated instruction, set
"TCP connection is not closed
after instruction completion" in
the close option of the control
data.
73D8
H
Failed to open the TCP
connection for the request
message transmission.
COM.ERR.
• Check whether the operation
status of the target device is
normal or not.
• Check the open status of the
target device.
• Review the IP address, port No.
setting and other parameters of
the target device.
• Check the line status for an
error.
73D9
H
Open failure
Since the normal connection
resources were all being used,
a new TCP connection could
not be opened.
COM.ERR.
• Retry after a little while.
• Decrease the number of TCP
connections used
simultaneously.
73DA
H
Alive check
failure
(KeepAlive
function)
Since the existence of the
target device could not be
confirmed by the KeepAlive
function, the TCP connection
was disconnected.
COM.ERR.
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
error.
7400
H
Target device
port No. error
The port number setting of the
target device is erroneous.
COM.ERR.
Review the port number setting of
the target device at the time of
transmission.
7401
H
Target device
IP address
error
The IP address setting of the
target device is erroneous.
COM.ERR.
Review the IP address setting of
the target device at the time of
transmission.
7402
H
Open
failure
A TCP connection was not
established in the open
processing.
COM.ERR.
• Check whether the operation
status of the target device is
normal or not.
• Check the open status of the
target device.
• Review the IP address, port No.
setting and other parameters of
the target device.
• Check the line status for an
error.
7403
H
Send error
A send error occurred.
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.
• Hardware fault.
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