Specifications

11
Q4ARCPU Redundancy
■
Redundancy PC network system
●
Existing PCs and Redundancy PCs can be combined on the same network.
Q4AR
CPU
Q4AR
CPU
AJ71
QLP21
AJ71
QLP21
AS92RA61RP A6RAF AS92R A61RP
AnU
CPU
AJ71
LP21
1Ns4
(
regular module
)
Power
supply
QnA
(
R
)
CPU
AJ71
QLP21
1Ns5
(
regular module
)
Power
supply
QnA
(
R
)
CPU
AJ71
QLP21
1Ns6
(
regular module
)
Power
supply
Q4AR
CPU
AJ71
QLP21
Power
supply
1Mp1
(
control module
)
1Ns2
(
regular module
)
1Ns3
(
regular module
)
Data tracking
Network
■
Compatible CPU modules
All of the QnA family of CPU modules from QnAS* to QnA
to Q4AR can be used with this redundancy configuration.
A smaller, low cost system can be configured for QnAS, and
a larger system with QnA and Q4AR modules.
*
The QnAS CPU is a compact sized CPU from the QnA series.
Please refer to the QnAS/AnS CPU catalog for more details.
Each CPU, however, knows the status and controls the
results of the other CPUs. A network device B/W can be
used for data exchange between the CPUs. Up to 2k bytes
of B/W can be sent from one CPU to the other every
network scan.
■
Operations
CPU: While the master CPU is normal and controlling
remote I/Os, the sub-master CPU is executing its program
and receiving remote I/O data via the network. Both CPUs
carry out their respective programs, but they are not
synchronized.
Master network module: Network modules of both the
master and the sub-master are active, but the sub-master
does not send data out to control remote I/Os when the
master CPU is in normal mode.
Local I/O: Local I/O modules can also be used, but they
cannot be controlled by the CPU module on the other side.
■
Exchange of data between CPUs
With this configuration each CPU runs its own programs.
Whether the sub-master runs a program to resume control
or not depends on the requirements of the application.
Master
PLC
Remote Remote Remote
Sub master
PLC
Master
PLC
B/W data
exchange
Remote Remote Remote
Sub master
PLC
■
Control switchover
Control switchover occurs when any of the following is
detected.
●
The power supply of the master PLC has gone down
●
The QnACPU on the master detects a fatal error that
makes it impossible for the CPU to continue operations.
●
The network module on the master is cut off from com-
munications
Note: The direction of switchover is always from the
master to the sub-master. Once control is switched over
from the master to the sub-master, the sub-master does not
switch back over to the master even if an error is detected.
When the master, then, is ready to be put back online, it is
recommended that both PLCs be reset as soon as possible.
■
Switchover time
Switchover time is as follows:
●
In the case of a power, CPU, or network module failure,
approximately 1 second is required to switch control.
●
In the case of a network cable disconnection, approxi-
mately 3 seconds are necessary to switch control.
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