8 - 9 8 - 9
MELSEC-GOT
8 ERROR CODES AND ERROR MESSAGES
(2) Error messages appearing due to faulty ACPU bus connection and
measure against errors
Cause and check point
Error
Code
Error
Messages
Check Timing
Error detail
Remedy
Corresponding
CPU
22
WDT ERR. When an End
instruction is
executed
(1) The scanning time exceeds
the calculation congestion
monitoring time.
(2) The scanning time may be
extended by waiting for a
response from an SP module
that is down, and errors may
occur simultaneously.
(1) Use the error history to check whether
simultaneous occurrence errors are
present.
(2) Refer to the SP module down check
points.
31
UNIT
VERIFY
ERR.
When an End
instruction is
executed
The information stored in the
cards of the module installed in
the base module and the
communication module of the
GOT is different from that read at
the initial time.
(If an error occurs on a module
(vacant) other than that installed
in the base module, the mis-
operation may be caused by
noise.)
Check the faulty module at special resisters
D9116 to D9123.
(1) Check that the module and the cables are
connected correctly.
(2) Check that the PLC and the GOT are
earthed correctly.
During execution of
FROM/TO
instruction set
When the FROM/TO instruction
is executed, an imprecise
response is returned from the
special function module
(including the GOT).
Check the faulty module from the error step.
(1) Check that the module and the cables are
connected correctly.
(2) Replace the faulty module with a new
one.
(3) Check that the PLC and the GOT are
earthed correctly.
40
CONTROL_
BUS ERR.
At CPU power ON/
At reset
At the time of initial
communication, an imprecise
response is returned from the
special function module
(including the GOT).
(1) Check that the module and the cables are
connected correctly.
(2) Because a faulty module cannot be
located, remove the modules one by one
until no CONTROL_BUS ERR. message
appears to indicate the module where the
error occurs.
(Because the modules are removed, SP.
UNIT ERR. message may appear. Stop
transmitting the FROM/TO instruction to
the applicable module.)
During execution of
FROM/TO
instruction set
The special function module was
accessed during the execution of
a FROM/TO instruction set, but
there was no response.
Check the faulty module from the error step.
(1) Check that the module and the cables are
connected correctly.
(2) Replace the faulty module with a new
one.
(3) Check that the PLC and the GOT are
earthed correctly.
41
SP. UNIT
DOWN
At CPU power ON/
At reset
At the time of initial
communication, a response is not
returned from the special function
module (including the GOT).
43
I/O INT
ERR.
During interrupt
An imprecise interrupt occurs to
the PLC CPU.
(1) Check that the module and the cables are
connected correctly.
(2) Replace the faulty module with a new
one.
(3) Check that the PLC and the GOT are
earthed correctly.
44
SP. UNIT
LAY ERR.
At CPU power ON/
At reset
Too many modules are installed
(see the PLC CPU specification).
(1) Check the number of installed modules.
(2) Check the number of extension stages
and the I/O slot numbers.
46
SP. UNIT
ERR.
During execution of
FROM/TO
instruction set
The FROM/TO instruction is
executed to any module other
than the special function module.
(1) Review the sequence program.
(2) Check the number of extension stages
and the I/O slot numbers.
ACPU
