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Checking Operations of CQM1 Master Units
Section 6-4
6-4-3
Checking Normal Operations Using Ladder Programming
This section provides information on how to write a ladder program to monitor
the operation of the CompoBus/S System and prohibit using the I/O data of
the Slaves in the system when an error occurs or the Slaves are not partici-
pating in the network correctly.
The CQM1 Master Unit does not have a status area but an alarm output ter-
minal (ALM) instead. The alarm output terminal is short-circuited if either of
the following errors occur. (Refer to page 117.)
• Area duplication error (ERS indicator is lit)
• Communications error (ERC indicator is lit)
It is recommended to write a program that enables the Input Unit to accept
alarm output and the I/O data of the Slaves in the network is used only when
the alarm output terminal is OFF.
6-4-4
Troubleshooting
The indicators of a Master Unit connected to a CQM1 PLC will indicate when
an error has occurred. Check the Master Unit’s indicators and perform the
error processing described in the following table.
When an error occurs in a Slave, the Slave can be identified from the status of
the Master’s indicators (refer to page 128) or from the status flags in the PLC’s
Special I/O Unit Area.
The alarm output can also be used to determine when an error has occurred.
Refer to
6-4-2 Error Detection with the Alarm Output (CQM1 Only)
for details.
Error
Probable cause
Possible remedy
The Master Unit’s RUN
indicator is OFF
The PLC’s power is OFF.
Turn the PLC’s power supply ON.
An I/O UNIT OVER error occurred in the
PLC.
Either change the PLC word allocation setting on
pins 1 and 2 of the DIP switch or remove another I/
O Unit.
An I/O BUS error occurred in the PLC
because the Master Unit is not connected
securely.
Turn the PLC OFF, make sure that the Master Unit
is mounted correctly, and then turn the PLC ON
again. Replace the Master Unit if the error recurs.
An I/O BUS error occurred in the PLC
because the PLC’s End Cover is not con-
nected securely.
Turn the PLC OFF, make sure that the End Cover
is mounted correctly, and then turn the PLC ON
again. Replace the Master Unit if the error recurs.
An I/O BUS error occurred in the PLC
because the PLC word allocation setting
(pins 1 and 2) was changed after communi-
cations were established.
Turn the PLC OFF and then ON again.
The Master Unit is faulty.
Replace the Master Unit.
The Master Unit’s SD
indicator is OFF
The same area may be allocated to more
than one Slave. (The Master Unit’s ERS
indicator will be ON at the same time.)
See the explanation under “The Master Unit’s
ERS indicator is ON.,” below.
The Master Unit is faulty.
Replace the Master Unit.