Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual page 651

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.
Item
Program execution Initial execution
type program
Scan execution type
program
Local device setting
File register setting
Direct access input (DX)
Direct access output (DY)
FROM/TO instructions
Instruction that requires several scans
For the operation of programs which are not set as both systems execution programs at system switching, refer to the
following.
Page 614 Operation at system switching
New control system CPU module
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.
This type of program is executed from the step 0.
This setting is in accordance with the parameter
settings.
The file register setting before system switching is
held.
In the program execution after system switching, data is fetched when an instruction using the direct access input
(DX) is executed.
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 652 Redundant System Operation Setting)
In the program execution after system switching, this instruction is executed when the instruction execution
condition is satisfied.
• 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.
New standby system CPU module
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.
This setting is in accordance with the parameter
settings.
The file register setting before system switching is
held.
37 FUNCTIONS
37.5 Program Execution in Both Systems
37
649