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Checking Operations of CQM1 Master Units
Section 6-4
6-4 Checking Operations of CQM1 Master Units
6-4-1 Indicators
Error Status The Master Unit’s indicators can indicate operating errors.
Note Check the system’s operation with just one Slave connected (one Slave at a
time) if the CompoBus system doesn’t operate but the Master’s indicator sta-
tus doesn’t match any of those in the following table.
Communications Error
Node Number Indicators
When a communications error occurs with a Slave during communications
and the ERC indicator lights or the ERS indicator lights or flashes, the other
indicators will show the node number of the Slave where the error occurred in
binary.
When several communications errors occur simultaneously, the node number
with the highest priority error will be displayed. The priority is as follows:
1,2,3... 1. Area overlap error (ERS lit)
2. Address over error (ERS flashing)
3. Communications error (ERC lit)
Situation Indicator status ALM
Output
Probable cause Possible remedy
RUN ERC ERS SD RD
Normal com-
munications
ON OFF OFF ON ON OFF --- ---
PLC’s power
OFF
OFF OFF OFF OFF OFF OFF The PLC’s power is OFF. Turn the PLC’s power sup-
ply ON.
I/O UNIT OVER
error
OFF OFF OFF OFF OFF OFF The PLC’s limit on I/O
points was exceeded by the
CompoBus/S Master Unit.
Reduce the PLC word allo-
cation setting or remove
one of the other Units.
I/O BUS error ON/
OFF
OFF OFF OFF OFF OFF The connection between
the CPU Unit and I/O bus is
not correct.
Check the mounting of each
I/O Unit and the End Cover.
Turn the PLC ON again
after correcting the cause of
the error.
Slave not con-
nected
ON OFF OFF ON OFF OFF No Slaves are connected,
or the communications
mode of each Slave does
not match that of the Master
Unit.
Use a Slave that can com-
municate properly, or make
the communications mode
of each Slave match that of
the Master Unit.
Data area over-
lap
ON --- ON OFF OFF ON When the “number of
points/node number” set-
ting is set to 4, this status
indicates that the same
area is allocated to more
than one Slave. Communi-
cations will be stopped.
Check the area allocated to
the 8-point Slave where the
error occurred, eliminate
the area overlap, and then
restart the PLC.
See Communications Error
Node Number Indicators
below.
Address over
error
ON --- Flashing ON ON OFF When the “PLC word allo-
cation” setting is 2 or 4
words, this status indicates
that an out-of-range node
number from 0 to 7 has
been set.
Check the indicators and
set the node number to an
acceptable value.
See Communications Error
Node Number Indicators
below.
Communica-
tions error with
a Slave
ON ON --- ON --- ON An error has occurred with
a Slave during communica-
tions and it is withdrawn
from the system.
Check the indicators and
clear the cause of the com-
munications error. See
Communications Error
Node Number Indicators
below.
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