Mitsubishi Electric Melsec QJ71LP21 Reference Manual page 34

1 OVERVIEW
Control system
1 - 13
(7) Redundant system configuration
(a) Network modules can be dualized.
A system containing a network module can be dualized (redundant system)
by installing another network module and using redundant CPUs.
In case of an error in the control system CPU or a network module, the
redundant system including double network modules switches the control
system to the standby system, allowing system control and data linking to
be continued on the standby system. (Refer to Section 7.10.1.)
(b) Automatically issuing system switching request to the control system CPU
If failure of a network module mounted to the control system CPU of the
redundant system or a data link error is detected, a system switching
request will be automatically issued to the CPU. (Refer to Section 7.10.5.)
(c) Transient transmission to redundant system is available.
By transient transmission using special link instructions or GX Developer,
device data can be read from or written to the host system, control/standby
system, or system A/B in the redundant system, and remote RUN/STOP
can be executed. (Refer to Section 7.4.5.)
When the redundant system is a target station, even if system switching
occurs, the target can be followed by specifying the CPU type of the station
to control or standby system.
MELSECNET/H PLC to PLC network
Standby system
MELSECNET/H remote I/O network
MELSEC-Q
1 - 13