P3: Basic PLC Program for SINUMERIK 840D sl
13.5 Starting up the PLC program
Basic Functions
858 Function Manual, 09/2011, 6FC5397-0BP40-2BA0
13.5.9 Troubleshooting
This section describes problems which may occur, their causes and remedies and should be read carefully
before hardware is replaced.
Errors, cause/description and remedy
Serial
no.
error
informati
on
Errors Cause/description To correct or avoid errors
1No
connection
via MPI to
PLC.
The MPI cable is not plugged in
or is defective. Possibly, the
STEP 7 software is also not
correctly configured for the MPI
card.
Test: Create a link with the
programmer in the STEP 7 editor by
means of connection "Direct_PLC". A
number of node addresses must be
displayed here. If they do not appear,
the MPI cable is defective/not plugged
in.
2 PLC cannot
be accessed
in spite of
PLC general
reset.
A system data block SDB 0 has
been loaded with a modified MPI
address. This has caused an
MPI bus conflict due to dual
assignment of addresses.
Disconnect all MPI cables to other
components. Create the link
"Direct_PLC" with the programmer.
Correct the MPI address.
3 All four LEDs
on the PLC
flash (DI
disaster)
A system error has occurred in
the PLC.
Measures:
The diagnostic buffer on the PLC
must be read to analyze the
system error in detail. To access
the buffer, the PLC must be
stopped (e.g. set "PLC" switch to
position 2). A hardware reset
must then be performed. The
diagnostic buffer can then be
read out with STEP 7. Relay the
information from the diagnostic
buffer to the Hotline /
Development Service. A general
reset must be carried out if
requested after the hardware
RESET. The diagnostic buffer
can then be read with the PLC in
the Stop state.
Once the PLC program has been
RESET or reloaded, the system may
return to normal operation. Even in this
case, the content of the diagnostic
buffer should be sent to the
Development Office.
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