Mitsubishi Electric MELSEC-Q Series User Manual page 283

Problem Check item
Cable or other
A4-1
parts
Power supply (for
A4-2
communications)
A station
cannot perform
data link
occasionally.
A4-3 Noise
A4-4 Startup
Failure of a slave
A4-5
station
Standby master
A4-6
station
Description
Are there no disconnection,
short circuit, incorrect wiring,
poor connection, and
coexistence of different
cables?
Do a transmission distance,
station-to-station distance,
transmission cable, and FG
terminal grounding meet the
specifications?
Are terminating resistors
connected?
Is the power on and is the
applied voltage within the
specified range?
Is the transmission cable free
from noise?
Has the faulty station started
in the correct procedure?
Do slave stations normally
operate?
Isn't the standby master
station controlling the data
link?
CHAPTER 11 TROUBLESHOOTING
Check method
Check cables connected to the
faulty station.
When faulty stations occur
sequentially to one end on the
transmission path, check cables
connected to faulty stations close
to the master station.
Check if terminating resistors are
connected to the both ends in the
CC-Link system.
Check if a station with built-in
terminating resistor is connected
other than at both ends in the CC-
Link system.
Check power supplied to the
faulty station.
Check if the transmission cable is
away from the power cable.
Check if the FG terminal is
grounded separately from the
GND terminal of the power
system.
Reduce the transmission speed
and check if the frequency of
occurrence of noise is reduced.
Check if the faulty station
normally starts in a different
procedure.
Replace modules on the faulty
station and check for operation.
Check if the standby master
station is not set as a station
controlling the data link by the
CC-Link diagnostics of the master
station.
Corrective action
Correct the wiring.
11
Connect terminating
resistors to the both
ends in the CC-Link
system.
Apply the voltage
within the specified
range.
Keep the transmission
cable away from the
power cable.
Ground the terminals
separately.
Take noise reduction
measures.
Reduce the
transmission speed.
Start the faulty station
in the procedure
described in the
manual for the station.
Repair or replace the
module on the faulty
station.
Reboot the system so
that the master station
will control the data
link.
281