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MELSEC-Q
11 TROUBLESHOOTING
Occurrence Error
Code
Error Name Description Lit LED Corrective Action
1) 2) 3) 4) 5)
7423H
7424H
7425H
7426H
7427H
7428H
7429H
742AH
742BH
742CH
ICMP error
packet
reception
The error packet of ICMP was
received.
COM.ERR.
• Review the setting of the router
information.
• Check whether the router
operates normally.
• Check the router
communication path for any
error.
• Check the communication path
ahead of the router for any
error.
• Review the IP address of the
target device at the time of
transmission.
• Check whether the target device
with the specified IP address
exists on the line or not.
• As the line may be busy, retry
after a little while.
• Review the IP reassembly timer
value of the target device.
742DH
Router relay
function error
• Without the routing
information setting of the
basic parameter, data were
attempted to be sent to the
target device that has a
different IP address class or
net ID.
• The routing information
setting of the basic parameter
is erroneous.
COM.ERR.
• Review the IP address of the
target device at the time of
transmission.
• Review the setting of the routing
information.
• Review the setting of the subnet
mask pattern.
7440H
UDP check
sum error
A check sum error was
detected in the UDP protocol.
COM.ERR.
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
error.
7450H
TCP ULP time-
out error
• The TCP ULP timer timed
out.
• ACK is not returned from the
target device.
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.
• Review the TCP ULP timer
value of the basic parameter.
7451H
TCP check
sum error
A check sum error was
detected in the TCP protocol.
COM.ERR.
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
error.
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