OPERATION MANUAL CompoBus/S

Checking Operations of CS-series and CJ-series Master Units Section 6-3
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.
376
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.
Usable node numbers setting is incorrect.
A common system mistake has been
made. (Refer to the table on page 376
for a list of common mistakes.)
Check the Active Node Flags for the Master and see whether
the flags are ON for all of the connected Slaves. If there is a
duplication, change the Slaves’ node number settings.
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 4-2-3 I/O Allocations or 4-3-4 I/O Allocations and
reset the usable node numbers to correct values.
Refer to the table on page 376 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 in a
system in which the main line must be distinguished 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.