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4.6.3 Switching from the scan execution type to the interrupt/fixed
scan execution type program
The CPU module performs the following when switching from the scan execution type program to the interrupt/fixed
scan execution type program.
• Saving and restoring the index register data
• Saving and restoring block numbers of the file register
(1) Setting for saving and restoration
Saving and restoration setting can be enabled in the PLC system tab of the PLC parameter dialog box.
To disable writing to the index register in the interrupt/fixed scan execution type program, select "High Speed
Execution" in the Interrupt Program/Fixed Scan Program Setting area.
If this setting is enabled, the program will switch faster than before.
(2) Processing of the index register
(a) When "High-speed execution" is not selected
• When switching from the scan execution type program to the interrupt/fixed scan execution type program
The CPU module saves index register values in the scan execution type program, and passes them to the
interrupt/fixed scan execution type program.
• When switching from the interrupt/fixed scan execution type program to the scan execution type program
The CPU module restores the saved index register values.
*1 The Z0 value is changed to 3 in the interrupt program.
To pass index register values from the interrupt/fixed scan execution type program to the scan execution type program, use
word devices.
Selecting this
saves or restores
index register data.
Execution program
Z0=1 Z0=1 Z0=3
*1
Z0=0
Z0=1
Passed
Switching
Saved
Restored
Restored
Z0=1 Z0=1 Z0=1
Z0=1
Save area of index register
Index register value
Scan execution
type program
Scan execution
type program
Interrupt/fixed scan
execution type
program
for scan execution
type program
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