Mitsubishi 900 Series User Manual page 107

(2) Error messages appearing due to faulty ACPU bus connection and measure against errors
Error Error
Check Timing
Code Messages
When an End
22 WDT ERR. instruction is exe-
cuted
When an End
UNIT VER-
31 instruction is exe-
IFY ERR.
cuted
During execution of
FROM/TO instruc-
tion set
CONTROL
40 _BUS
ERR.
At CPU power ON/
At reset
During execution of
FROM/TO instruc-
tion set
SP. UNIT
41
DOWN
At CPU power ON/
At reset
I/O INT
43 During interrupt
ERR.
SP. UNIT At CPU power ON/
44
LAY ERR. At reset
During execution of
SP. UNIT
46 FROM/TO instruc-
ERR.
tion set
9 - 10
9.4 Troubleshooting in bus connection
9.4.1 Locating error positions
Error detail
(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.
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-opera-
tion may be caused by noise.)
When the FROM/TO instruction is
executed, an imprecise response
is returned from the special func-
tion module (including the GOT).
At the time of initial communica-
tion, an imprecise response is
returned from the special function
module (including the GOT).
The special function module was
accessed during the execution of a
FROM/TO instruction set, but
there was no response.
At the time of initial communica-
tion, a response is not returned
from the special function module
(including the GOT).
An imprecise interrupt occurs to
the PLC CPU.
Too many modules are installed
(see the PLC CPU specification).
The FROM/TO instruction is exe-
cuted to any module other than the
special function module.
Cause and check point
Remedy
(1) Use the error history to check whether
simultaneous occurrence errors are
present.
(2) Refer to the SP module down check
points.
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.
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.
(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.)
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.
(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.
(1) Check the number of installed modules.
(2) Check the number of extension stages
and the I/O slot numbers.
(1) Review the sequence program.
(2) Check the number of extension stages
and the I/O slot numbers.
Correspond-
ing CPU
ACPU