408
26 BASIC CONCEPT
26.5 Operation Modes of the Redundant System
26.5
Operation Modes of the Redundant System
A redundant system operates in one of the following two modes.
A redundant system is started in the backup mode. To switch the operation mode, use the engineering tool. (
Operation Mode Change)
The following table describes differences between the backup mode and the separate mode.
Operation mode
Description
Backup mode
A mode used to normally operate the redundant system.
When an error or failure has occurred in the control system, the standby system is switched to the control system to continue the
operation. Even if a system failure has occurred in the control system, the standby system of the redundant system continues the
operation because data is transferred from the control system to the standby system at every scan.
Separate mode
A mode used to maintain the redundant system without stopping controls.
In separate mode, the control system CPU module and the standby system CPU module can execute different programs. The
program of the standby system can be modified and the operation of the program can be checked with the data tracked from the
control system while the system is being controlled in the control system.
Item
Backup mode
Separate mode
Program operation
The control system executes programs.
The standby system CPU module executes programs according
to "Both Systems Program Executions Setting" in "Program
Setting" of "CPU Parameter". With the default setting, the
standby system does not execute programs.
To switch the mode to the backup mode, refer to the following.
Page 439 Mode switching to the backup mode
Both of the control system and the standby system execute
programs.
To switch the mode to the separate mode, refer to the following.
Page 438 Mode switching to the separate mode
System switching
Automatic system switching and manual system switching are
supported.
Only manual system switching is supported.
Tracking transfer
Data is transferred according to "Tracking Setting" of "CPU
Parameter".
Data is transferred according to "Tracking Setting" of "CPU
Parameter".
However, the following data causes tracking transfer to stop.
• Local devices, local labels
• Special relay, special register
• PID control instruction information
• Signal flow memory
Memory copy from
control system to
standby system
The following copy operations can be performed.
• Automatic memory copy
• Memory copy with the engineering tool
• Memory copy with the special relay and special register
The following copy operations can be performed.
• Memory copy with the engineering tool
• Memory copy with the special relay and special register
System consistency
check
The system consistency check is performed.
The system consistency check is not performed.
Program execution type
■
When the operation mode is changed to the backup mode
The control system and the standby system take over their
execution types before the operation mode change.
■
When the operation mode is changed to the separate mode
The control system and the standby system operate differently.
• The control system takes over its execution type before the
operation mode change.
• The standby system operates in the execution type specified
by the CPU parameter.
Interrupt program
execution enable/disable
status
■
When the operation mode is changed to the backup mode
The control system and the standby system take over their
execution enable status before the operation mode change.
■
When the operation mode is changed to the separate mode
The control system and the standby system operate differently.
• The control system takes over its execution enable status
before the operation mode change.
• The standby system disables execution of interrupt programs.
I/O refresh
Whether or not to refresh the output (Y) of the standby system
depends on "Standby System Output Setting" of "CPU
Parameter".
With the default setting, the output (Y) of the standby system is
not refreshed.
Even though "Standby System Output Setting" has been set to
"Disable" in "CPU Parameter", the output (Y) of the standby
system is enabled.
Link refresh
Data is not transferred from devices of the CPU module in the
standby system to link devices.
Data is transferred from devices of the CPU module in the
standby system to only the link special relay (SB) and link
special register (SW). (Except for CC-Link)
Writing data to the
programmable controller
Data can be written to both systems. Or, data can be written to
only a system specified in the connection destination setting.
Data is written to only a system specified in the connection
destination setting.
Remote operation
function
Remote operations can be performed on both systems.
Remote operation with the engineering tool can be performed
only on a system specified in the connection destination setting.
Time synchronization
Time of the standby system is synchronized with that of the
control system.
Time of both systems is not synchronized.
Содержание MELSEC iQ-R-R00CPU
Страница 2: ......
Страница 151: ...9 MONITOR FUNCTION 9 1 Real Time Monitor Function 149 9 MEMO ...
Страница 323: ...18 SEQUENCE SCAN SYNCHRONIZATION SAMPLING FUNCTION 321 18 MEMO ...
Страница 330: ...328 20 ROUTING SETTING 20 3 Precautions MEMO ...
Страница 423: ...26 BASIC CONCEPT 26 8 State Transition of the Redundant System 421 26 MEMO ...
Страница 524: ...522 30 MAINTENANCE AND INSPECTION FOR A REDUNDANT SYSTEM 30 1 Module Replacement in the Redundant System MEMO ...
Страница 1009: ...APPX Appendix 14 List of Available SQL Commands for CPU Module Database Access Function 1007 A MEMO ...
Страница 1014: ...1012 APPX Appendix 15 Added and Enhanced Functions MEMO ...
Страница 1027: ......