Mitsubishi Electric melsec q00ujcpu User Manual page 396

(b) When "High-speed execution" is selected
1) When switching from the scan execution type program to the interrupt/fixed scan
execution type program
The CPU module does not save/restore any index register values.
2) When switching from the interrupt/fixed scan execution type program to the scan
execution type program
If data are written to the index register by the interrupt/fixed scan execution type program, the values of the
index register used in the scan execution type program will be corrupted.
Execution program
Index register value
Save area of index register
for scan execution
type program
Figure 9.63 Saving and restoring index register data (when "High speed execution" is selected)
*1: The Z0 value is changed to 3 in the interrupt program.
When writing data to the index register by the interrupt/fixed scan execution type program, use the ZPUSH or
ZPOP instruction to save and restore the data.
SM400
I0
SM400
Figure 9.64 Writing data to the index register in the interrupt/fixed scan execution type program
Interrupt/fixed scan
Switching
Scan execution
execution type
type program
program
Passed
Z0=1
Z0=1
Z0=0 Z0=0
ZPUSH
ZPOP
IRET
Restored
Scan execution
type program
Passed
*1
Z0=3
Z0=3
Z0=0 Z0=0 Z0=0
Data in Z0 to Z15 are
D0
stored in the area
addressed from D0.
Data in the area
D0
addressed from D0 are
stored in Z0 to Z15.
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