Mitsubishi Electric Melsec QJ71LP21 Reference Manual page 79

3 SPECIFICATIONS
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(6) Station detach function (coaxial bus system and twisted bus
system)
In the coaxial bus system and twisted 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
Control station Normal station
(station No. 1) (station No. 2)
Terminating resistor
(b) When abnormal
The data link continues excluding the station that is down.
Control station Normal station
(station No. 1) (station No. 2)
POINT
When a cable disconnection occurs, the data link cannot be performed because
there will be no terminating resistors.
Control station
(station No. 1)
In addition, even if the cable is normal, the data link cannot be performed if a
terminating resistor is detached.
Normal station Normal station
(station No. 3) (station No. 4)
Terminating resistor
Down
Normal station Normal station
(station No. 3) (station No. 4)
Normal station Normal station
(station No. 2) (station No. 3)
Cable disconnection
MELSEC-Q
Normal station
(station No. 4)
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