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5.1 Basic Concept of Redundant System
5.1.2 Determination of Control System and Standby System
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REDUNDANT SYSTEM FUNCTIONS
5.1.2 Determination of Control System and Standby System
In a redundant system, either system CPU module runs the programs, controls the system
and communicates with the network.
The system that includes the CPU module running the programs is referred to as the
"Control system".
The other system serves as a backup for continuing the system operation in the case the
module on the control system fails or develops an error.
This backup system is referred to as the "standby system".
The standby system CPU module does not run the programs. (The same status as the
STOP status.)
The control system and standby system are determined by which system starts up first, or
which RESET/L.CLR switch of the CPU module is set to the neutral position first.
(1) When One of the Systems Starts Up Before the Other One
*1 *2
If either system A or system B starts up before the other one, the system that starts up
first will be the "Control system", and the other one will be the "Standby system".
*3
When both CPU modules of the system A and system B are reset, the system with the
CPU module of which RESET/L.CLR switch is set to the neutral position first will be
the "Control system", and the other one will be the "Standby system".
*3
(a) When system A starts up first
* 1: Refer to Section 5.1.1 for determination of system A and system B.
* 2: Indicates the case where one system starts up within 3 seconds after the other system.
* 3: If the second system does not start up within 3 seconds of the first one, the "STANDBY
SYS.DOWN(error code: 6300)" continuation error will occur in the control system CPU module.
By disabling "Check standby system malfunction," at the standby System Monitor settings in the
redundant parameter operation mode settings with GX Developer, the control system will not
detect the "STANDBY SYS. DOWN" continuation error.
Diagram 5.4 Control System and Standby System when System A Starts Up First
System A
System B
Tracking cable
Control system
Standby system
1), 2) show the powerup
procedure.
1) Turn on the power for System A. 2) Turn on the power for System B.