Mitsubishi Electric MELSEC-Q Series User Manual page 199

10 DEVICES
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(2) When the "High-speed execution" check box is ON:
(a) If a main routine/sub-routine program is switched to an interrupt program,
index register data will not be saved/restored.
(b) If data is written onto index registers by using an interrupt program, the
values of index registers used for an main routine/sub-routine program will
be corrupted.
Executed program
Index register value
Index register storage area
(c) Before writing data onto index registers by using an interrupt program, use
the ZPUSH/ZPOP instruction to save/restore the data.
SM400
I0
SM400
Switch-
Main routine/
ing
sub-routine
Interrupt program
program
Transf-
erred
Z0=1
Z0=0 Z0=0
ZPUSH
ZPOP
MELSEC-Q
Reset
Transf-
erred
Z0=1 to Z0=3
Z0=0 Z0=0
: For interrupt program, Z0 is changed to 3.
The points after D0 store the
D0
data (Z0 to Z9).
The data after D0 is stored
D0
in points (Z0 to Z9).
IRET
Main routine/
sub-routine
program
Z0=3
Z0=0
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