Loopback Function - Mitsubishi Electric MELSEC iQ-R Series User Manual

Loopback Function

This function continues data link with normal stations even if a cable disconnection or faulty station occurs.
At the time of cable disconnection
Even if a cable disconnection occurs, the system automatically performs loopback to continue the data link.
Control station Normal station
(station No.1) (station No.2)
Normal station Normal station
(station No.6) (station No.5)
• When loopback is being performed due to cable disconnection, both the forward loop and reverse loop may
be considered normal depending on the cable disconnection condition. Whether the forward loop or reverse
loop is normal or abnormal is determined by the reception status of the loopback station.
• If the cable is connected after being disconnected, the line to be used (forward loop/reverse loop) may be
switched, but the data link is performed normally.
Occurrence of faulty stations
The system disconnects faulty stations and automatically performs loopback to continue the data link.
If two or more faulty stations occur, a station located between the faulty stations cannot perform data link. However, when
more than one station exists between the faulty stations, a normal station with a smaller station number is changed to a sub-
control station and continues data link.
Control station Normal station
(station No.1) (station No.2)
Loopback station
Down
Down
Normal station
(station No.6) Normal station
Loopback station (station No.5)
Disconnection
Normal station
(station No.3)
Normal station
(station No.4)
Sub-control station
(station No.3)
Loopback station
Normal station
(station No.4)
Loopback station
1
1 FUNCTIONS
43
1.3 RAS