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28 FUNCTIONS
28.6 Program Execution in Both Systems
Operation at system switching
The operation at system switching is different for a program executed in both systems. The following table shows the
operation at system switching.
For the operation of programs which are not set as both systems execution programs at system switching, refer to the
following.
Page 446 Operation at system switching
Item
New control system CPU module
New standby system CPU module
Program execution
Initial execution
type program
When an initial execution type program has not been
completed on the old control system at system
switching, it is executed again from its head.
When an initial execution type program has not been
completed on the old control system at system
switching, it is not executed on the new standby
system because system switching is performed after
the program completion on the old control system.
Scan execution type
program
This type of program is executed from the step 0.
Direct access input (DX)
In the program execution after system switching, data is fetched when an instruction using the direct access input
(DX) is executed.
Direct access output (DY)
Data is not output.
However, data is output when "Standby System Output Setting" of the CPU parameter is enabled and an
instruction using the direct access output (DY) is executed in the program execution after system switching. (
Page 485 Redundant System Operation Setting)
FROM/TO instructions
In the program execution after system switching, this instruction is executed when the instruction execution
condition is satisfied.
Instruction that requires several scans
• In the program execution after system switching, this instruction is executed when the instruction execution
condition is satisfied.
• When the systems are switched while the instruction is being executed, the instruction execution continues
and the completion device turns on at a completion of the instruction execution.
Summary of Contents for MELSEC iQ-R-R00CPU
Page 2: ......
Page 151: ...9 MONITOR FUNCTION 9 1 Real Time Monitor Function 149 9 MEMO ...
Page 323: ...18 SEQUENCE SCAN SYNCHRONIZATION SAMPLING FUNCTION 321 18 MEMO ...
Page 330: ...328 20 ROUTING SETTING 20 3 Precautions MEMO ...
Page 423: ...26 BASIC CONCEPT 26 8 State Transition of the Redundant System 421 26 MEMO ...
Page 1014: ...1012 APPX Appendix 15 Added and Enhanced Functions MEMO ...
Page 1027: ......