OPERATION MANUAL CompoBus/S

Checking Slave Operations Section 6-5
The indicators on the
Master and Slaves are
normal, but there are
errors in the communications
data
Common Mistakes The following table shows common connection mistakes and their remedies.
6-5 Checking Slave Operations
6-5-1 Indicators
382
Error Probable cause Possible remedy
The same node number is set on two or
more Input Slaves or Output Slaves.
The PLC’s Output OFF Bit is ON, so the
Output Slave outputs are always OFF.
The communications power supply to the
Slaves is ON, but the I/O power supply is
OFF, so the Output Slave outputs and Input
Slave inputs are always OFF.
There is a problem with the communication
cable connection or the cable itself.
The setting of the number of words allocated
to the PLC, or the number of points
allocated to a single node number is incorrect.
An Analog Terminal is connected to a
CQM1-SRM21 (without V1).
A common system mistake has occurred.
(Refer to the table on page 382 for a list of
common mistakes.)
Change one of the Slave’s node number settings
to eliminate the duplication, turn the Slave ON
again, and then turn the PLC ON again.
Turn OFF the PLC’s Output OFF Bit.
Provide an I/O power supply to the Slaves.
Check the connections and cable. Replace the
communications cable if it is faulty.
Refer to 4-4-3 I/O Allocations in CQM1 PLCs and
correct the number of words allocated to the PLC
or the number of points allocated to a single node
number.
Change the Master Unit to a CQM1-SRM21-V1.
Refer to the table on page 382 for common mistakes
and their remedies.
The Master or a Slave Unit is faulty. Replace the Slave Unit. Replace the Master Unit if
the problem recurs.
Mistake Remedy
A terminator is not connected. Connect a terminator (connector or terminal-block) at the
end of the cable farthest from the Master.
The terminator is not connected at the end of the cable farthest
from the Master.
The master is not connected at one end of the main line of
the system that has the main line distinguishable from the
branch lines.
The length of the main line, a branch line, or the total length
of the branch lines of the system in which the main line must
be distinguished from the branch lines is not within specifications.
The total communications cable in the system in which the
main line does not need to be distinguished from the branch
lines is not within specifications.
2-conductor VCTF cable, 4-conductor VCTF cable, and
Special Flat Cable are used together in the same system.
Connect the terminator at the end of the cable farthest from
the Master.
Connect the Master at one end of the main line.
Make sure that the lengths of the cables in the system are
within the specifications listed in 2-2-2 Maximum Cable
Length, or change the communications mode to Long-distance
Communications Mode so that the length of the
cables in the system will be within specifications.
Refer to 2-2-2 Maximum Cable Length and change the configuration
so that the length of the total communications
cable length will be within specifications.
Use just one kind of cable in the system.
There is a break in the communications cable. Reconnect or replace the communications cable.
When 4-conductor VCTF cable or Special Flat Cable is
being used, a connector is not attached securely to the
cable.
Make sure that the connectors are crimped correctly on the
cable.
A connector is faulty. Replace the faulty connector.
This section explains the indicators common to all of the Slave Units. In addition
to these common indicators, Slaves have other indicators, such as indicators
that reflect the status of the Slave’s I/O point. Refer to SECTION 5 Slave
Specifications and Operations for details on the indicators specific to each
Slave.