37  FUNCTIONS
37.1  System Switching
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*1 The operation varies in a program executed in both systems. ( Page 649 Operation at system switching)
*2 The safety program may be executed multiple times up until safety output is performed from the CPU module to the network module.
Local device setting (standard/safety program) This setting is in accordance with the parameter settings. No operation is performed because the program 
does not operate.
*1
File register setting The file register setting before system switching is held.
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) In the program execution after system switching, data is 
output when an instruction using the direct access output 
(DY) is executed.
FROM/TO instructions In the program execution after system switching, this 
instruction is executed when the instruction execution 
condition is satisfied.
No operation is performed because the program 
does not operate.
*1
Instruction that requires several scans • This instruction is executed in the program execution 
after system switching.
• When the systems are switched while the instruction is 
being executed in a program executed in both 
systems, the instruction execution continues and the 
completion device turns on at a completion of the 
instruction execution.
• No operation is performed because the 
program does not operate.
*1
• When the systems are switched while the 
instruction is being executed, the instruction 
execution continues. However, the 
completion device does not turn on in the new 
standby system, and it turns on in the control 
system after the next system switching.
*1
Constant scan Constant scan is enabled. Constant scan is disabled.
Item New control system CPU module New standby system CPU module