Mitsubishi Electric Melsec QJ71LP21 Reference Manual page 143

4 SETUP AND PROCEDURES BEFORE STARTING THE OPERATION
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(b) Mode setting for the forward loop/reverse loop test on the redundant
system
To perform the forward loop/reverse loop test on the redundant system, set
the operation mode of the redundant CPU to backup mode.
If the power to both systems cannot be turned on or off, perform the
forward loop/reverse loop test in separate mode.
1) When designating the redundant system as the testing station
The table below shows the mode settings for the case where the
redundant system is specified as a testing station.
Station performing
Redundant system
the test
Redundant system
Station not
performing the test
Non-redundant system station
The following shows the setting where system A (station No. 1) of the
redundant system (in backup mode) is specified as a station
performing the forward loop test.
Q25H Station
CPU No. 4
Control system
(system A)
Redundant Station
CPU No. 1
Set "Forward loop test" for the mode of
system A (station No. 1).
Set station
In backup mode
In separate mode
In backup mode
In separate mode
Set "online" for the mode of non-redundant
stations not performing the test
(station Nos. 3 and 4).
Q25H
CPU
Standby system
(system B)
Redundant
CPU
Set "Offline" for the mode of system B
(station No. 2).
MELSEC-Q
Description of setting
Set "Forward loop test" or
"Reverse loop test."
Set "Offline."
Set "Online."
Set "Online."
Station
No. 3
Station
No. 2
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