Station Detach Function (Coaxial Bus System) - Mitsubishi Electric MELSEC Q Series Reference Manual

3 SPECIFICATIONS
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REMARKS
If the network module has become faulty, a loopback may not be made depending
on the fault.
In that case, the network may stop. Identify the faulty network module in the
following method.
(1) Check the indicator LEDs (RUN LED off, ERR. LED on) of all network modules
for a faulty station.
(2) Power off all stations and power them on in order, starting from the remote
master station. At that time, check up to which station the network operates
properly.
Change the network module where the fault has been detected, and confirm that the
network is restored to normal.

(5) Station detach function (coaxial bus system)

In the coaxial bus system, even if the power to a connected station is turned off,
the data link continues between other stations which are still able to perform data
communication.
(a) When normal
Remote Remote I/O
master station station
(station No. 0) (station No. 1)
Terminating resistor
(b) When abnormal
The data link continues excluding the station that is down.
Remote Remote I/O
master station
(station No. 0) (station No. 1)
POINT
When a cable disconnection occurs, the data link cannot be performed because
there will be no terminating resistors.
In addition, even if the cable is normal, the data link cannot be performed if a
terminating resistor is detached from an F-type connector.
Remote I/O Remote I/O
station station
(station No. 2) (station No. 3)
Terminating resistor
Down
Remote I/O Remote I/O
station station
(station No. 2) (station No. 3)
Remote Remote I/O
master station station
(station No. 0) (station No. 1) (station No. 2)
Cable disconnection
station
Remote I/O Remote I/O
station station
(station No. 3)
MELSEC-Q
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