Mitsubishi Electric MELSEC-Q Series User Manual page 282

Problem Check item
Cable or other
A3-1
parts
Parameter
A3-2
setting
Power supply (for
A3-3
communications)
Data link
cannot be
performed in
the entire
system
A3-4 Noise
occasionally.
Failure of the
A3-5
master station
A3-6 Link stop
280
Description
Are cables and connectors
securely connected and do
they meet specifications?
Isn't the sequence scan time
long in the synchronous
mode?
Is the power on and is the
applied voltage within the
specified range?
Is the transmission cable free
from noise?
Do modules on the master
station normally operate?
Is Data link stop instruction
correctly executed?
Check method
Check cables between the master
station and slave stations.
Check if the sequence scan time
is within the allowable range.
10Mbps: 50ms
5Mbps: 50ms
2.5Mbps: 100ms
625kbps: 400ms
156kbps: 800ms
Check power supplied to the
master station and all slave
stations.
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.
Replace the modules and check if
the station normally operates.
Check if Data link stop (SB0002)
is off.
Corrective action
Correct the wiring.
Set the asynchronous
mode or reduce the
transmission speed.
Apply the voltage
within the specified
range.
Keep the transmission
cable away from the
power cable.
(Keep a distance of
100mm or more is
recommended.)
Ground the terminals
separately.
Take noise reduction
measures.
Reduce the
transmission speed.
Repair or replace the
module on the master
station.
Do not turn on Data
link stop (SB0002).
Do not write data to the
refresh source device
of Data link stop
(SB0002) from multiple
locations.
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