2
-
9
(b) Restrictions on programming
1) PLS and PLF instructions
The PLS and PLF instructions perform off processing in the next scan of which the instruction is executed.
Therefore, the device which is turned on by the instruction remains on until the same instruction is
reexecuted.
2) EI and DI instructions
During execution of an interrupt program, interrupts are disabled (DI) so that any other interrupt processing
will not be executed.
Do not execute the EI or DI instruction during interrupt program execution.
3) Timer (T) and counter (C)
Do not use the timer (T) and counter (C) in interrupt programs.
If more than one interrupts occur in one scan, the timer (T) and counter (C) in the interrupt program cannot
measure the time correctly.
The OUT C instruction status causes the counter (C) not to measure the number of interrupts correctly.
4) Instructions not available in interrupt programs
Refer to sections corresponding to each instruction in the following.
MELSEC-Q/L Programming Manual (Common Instruction)
Figure 2.10 Device turned on by the PLS instruction in the interrupt program
X0
OFF
ON
M0
OFF
ON
0
IO IRET END
END
0
END
END
0 IO IRET
0
PLS M0
X0
PLS M0
X0
Turns off by executing the
PLS M0 instruction.
Turns on by executing the PLS M0 instruction at the rise of X0.
