Omron SYSMAC CJ1W-PRM21, Operation Manual

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Troubleshooting I/O Communication
Section 7-3
7-3 Troubleshooting I/O Communication
This section deals with troubleshooting the I/O communication on the network
from a behavior point of view. The column on the left describes the general
perceived problem to the user. The columns on the right list the possible
causes and their remedies.
Communication Problems
Problem Probable cause Correction
PROFIBUS-DP Master Unit
is configured, but none of
the slaves are exchanging
data. No power is supplied to the system.
• All LED indicators on the system are OFF.
• Verify that power is supplied to the system.
A PLC CPU (startup) error occurred.
• The ERH indicator is ON, the other LED
indicators are OFF.
• The ERR/ALM LED indicator on the PLC
CPU is ON.
• Determine error in the PLC CPU (Refer to
the CS1 Series CPU Unit Operation Man-
ual (W339) or the CJ Series CPU Unit
Operation Manual (W393)).
The stored configuration contains a check-
sum error (storing configuration was inter-
rupted or failed).
• After restarting the Unit, the ERC LED indi-
cator is ON, and the PRM LED indicator is
OFF.
• Unit Status error flag may provide more
information (CIO Word n+4, bit 06, bit 07,
bit 09, see Note).
• Re-download the configuration.
• If the problem persists, replace the Unit.
The configuration contains timing errors.
• After restarting the Unit, the ERC LED indi-
cator is ON, and the PRM LED indicator is
OFF.
• Verify that the Bus parameter sets are cor-
rect.
• Re-download the configuration.
• If the problem persists, replace the Unit.
The PROFIBUS-DP Master Unit is in either
OFFLINE or STOP mode.
• The BST LED indicator is OFF
The Unit may have been configured to
maintain its current mode (last mode was
OFFLINE, during download).
• The BF LED indicator is ON: A PROFIBUS
interface error has occurred: see Master
Status 2 error flags (CIO Word n+6, bit 00 ~
03, see Note) for details.
Determine the mode of the Unit: Check the
Master Status 1 Word (CIO Word n+5, bit 00
to bit 03, see Note). If Unit is in OFFLINE or
STOP mode:
• Verify that the Master does not use the
same address as another Master Unit on
the network. Otherwise, correct the Master
Unit’s PROFIBUS address.
• Set CLEAR or OPERATE switch in CIO
Word n (see Note).
• Change the configuration to set the Unit
OPERATE mode when switching the PLC
to RUN/MONITOR mode (see Master DTM,
Master Setup Tab). Download the configu-
ration, and switch the PLC to RUN/MONI-
TOR mode.
Network cabling is not correct.
• BF LED indicator is ON.
• Master Status 2 error flag may provide
more information (CIO Word n+6, bit 00 ~
03, see Note).
• CIO Words n+9 to n+16 show which slaves
have problems.
Verify that the network installation is correct:
• Verify that all slaves are powered up and
functioning correctly.
• Verify that all slave stations are correctly
connected to the network.
• Verify that any repeaters used are function-
ing correctly.
• Check the cable length versus the selected
baud rate.
• Verify that any stubs used are not too long.
• Verify that termination (resistors and induc-
tors) are properly set and used.