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MELSEC-Q
11 TROUBLESHOOTING
Occurrence
Error
Code
Error Name
Description
Lit LED
Corrective Action
1) 2) 3) 4) 5)
7404
H
A receive error occurred.
COM.ERR.
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
error.
• Hardware fault.
7405
H
Receive error
The internal receive buffer has
no free space.
COM.ERR.
• Retry after a little while.
• Check whether the operation
status of the target device is
normal or not.
• Check the line status for an
error.
• Hardware fault.
7410
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.
7420
H
Broadcast
address
specification
error
The broadcast address was
specified in TCP-based
transmission.
COM.ERR.
Review the IP address setting of
the target device at the time of
transmission.
7421
H
Ethernet
address error
The Ethernet address of the
target device is unknown.
COM.ERR.
• 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.
• 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.
• Replace the target device with
the one having the ARP
function.
7422
H
IP check sum
error
A check sum error was
detected in the IP 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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