Mitsubishi Electric MELSEC-Q Series User Manual page 47

4 SEQUENCE PROGRAM CONFIGURATION & EXECUTION
CONDITIONS
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(5) Program creation restrictions
(a) A device which is switched ON by a PLS instruction in an interrupt program
will remain ON until the PLS instruction for the same device is executed
again.
END 0 IO IRET END 0
ON
X0 OFF
ON
M0 OFF
(b) During execution of the interrupt program, interrupts are disabled (DI) so
that other interrupt processing is not performed.
Do not execute EI/DI instructions in the interrupt program.
(c) Timers cannot be used in interrupt programs.
As timers are used at OUT T
switch contacts ON and OFF, the use of a timer in the interrupt program
would make a normal time count impossible.
(d) The following instructions cannot be used in interrupt programs.
• COM
• ZCOM
(e) When the interrupt program is executed when measuring time such as the
scan time or execution time, the measured time will become the value
obtained by adding the interrupt program/constant cycle execution type
program.
Thus, if the interrupt program is executed, the values stored in the following
special registers and GX Developer monitor values will become longer than
when the interrupt program is not executed.
1) Special registers
• SD520, SD521: Current scan time
• SD524, SD525: Minimum scan time
• SD526, SD527: Maximum scan time
• SD540, SD541: END processing time
• SD542, SD543: Constant scan wait time
2) GX Developer monitor values
• Execution time measurement
• Scan time measurement
• Constant scan
X0
PLS M0
END 0 IO IRET END
Switched ON by PLS M0 instruction at X0 leading edge (OFF to ON)
instructions to update present values and
MELSEC-Q
X0
PLS M0
0
Switched OFF by PLS M0 instruction
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