Loopback Function - Mitsubishi Electric MELSEC Q Series Reference Manual

4.4.2

Loopback function

This function isolates a disconnected cable or faulty station from the network, so that data link can be continued among
normally operating stations.
(1) Cable disconnection
Data link is continued even if a cable is disconnected.
Although the CC-Link IE Controller Network uses 2 core cables, loopback occurs even if a disconnection or an error is
detected on one side. (Transmissions using one side only are not performed.)
(2) Station failure
Data link is continued except for a faulty station.
If two or more stations go down, a station located between the faulty stations cannot perform data link.
However, when more than one station exist between the faulty stations, a normal station is changed to a sub-
control station and continues data link.
Disconnection
Control station Normal station
No.1 No.2
Normal station Normal station
No.6 No.5
Control station Normal station
No.1 No.2
Down
Loopback station
Normal station Down
No.6
Normal station
Loopback station
No.5
Normal station
No.3
Normal station
No.4
Sub-control station
No.3
Loopback station
Normal station
No.4
Loopback station
CHAPTER 4 FUNCTIONS
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