Panasonic FP-E Programming Manual page 1065

4.3.3 Precautions when Using a Control Instruction
Instructions which leading edge detection compare the condition of the previous
execution and the condition of the current execution, and execute the instruction only
if the previous condition was off and the current condition is on. In any other case, the
instruction is not executed.
When a leading edge detection instruction is used with an instruction which changes
the order of instruction execution such as MC, MCE, JP or LBL, the operation of the
instruction may change as follows depending on input timing. Take care regarding this
point.
Example 1: Using the DF instruction between MC and MCE instructions
Time chart 1
Time chart 2
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X0
X1
DF
X0
X1
Y10
Previous
execution of
DF instruction
X0
X1
Y10
Previous
execution of
DF instruction
4.3
MC 0
Y10
MCE 0
The input condition (X1) for the DF
instruction has not changed since the
time of the previous execution, thus
differential output is not obtained.
The input condition (X1) for the DF
instruction has changed from off to on
since the time of the previous execution,
thus differential output is obtained.
Leading Edge Detection Method
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