376
Checking Operations of CS-series and CJ-series Master Units
Section 6-3
Common Mistakes
The following table shows common connection mistakes and their remedies.
The indicators on
the Master and
Slaves are nor-
mal, but there are
errors in the com-
munications data
The same node number is set on two
or more Input Slaves or Output
Slaves.
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.
The PLC’s Output OFF Bit is ON, so
the Output Slave outputs are always
OFF.
Turn OFF the PLC’s Output OFF Bit.
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.
Provide an I/O power supply to the Slaves.
There is a problem with the communi-
cation cable connection or the cable
itself.
Check the connections and cable. Replace the communica-
tions cable if it is faulty.
Usable node numbers setting is incor-
rect.
Refer to
and
reset the usable node numbers to correct values.
A common system mistake has been
made. (Refer to the table on page 376
for a list of common mistakes.)
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 prob-
lem recurs.
Error
Probable cause
Possible remedy
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 far-
thest from the Master.
Connect the terminator 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.
Connect the Master at one end of the main line.
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 specifi-
cations.
Make sure that the lengths of the cables in the system are
within the specifications listed in
, or change the communications mode to Long-dis-
tance Communications Mode so that the length of the
cables in the system will be 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.
figuration so that the length of the total communications
cable length will be within specifications.
2-conductor VCTF cable, 4-conductor VCTF cable, and
Special Flat Cable are used together in the same system.
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.
