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Chapter 4. Ladder Diagram (LD) Programming
F_TRIG Operation
When the CLK input goes from true to false, the output Q is
true for one function block instance execution. The output Q
CLK
then remains false until a new falling edge is detected.
When the Controller transitions from STOP Mode to RUN
Mode and the CLK input is false and the instance memory is
Q
non-retentive, the output Q is true after the function block's
first execution. After the next execution, the output is false.
The F_TRIG output Q will be true for one function block
instance execution at a STOP Mode to RUN Mode transition
Function Block Execution
after the first download, whether or not instance memory is
retentive.
R_TRIG Operation
When the CLK input transitions from false to true, the
output Q is true for one function block execution. The
CLK
output Q then remains false until a new rising edge is
detected.
When the Controller transitions from STOP Mode to
Q
RUN Mode and the CLK input is true and the instance
memory is non-retentive, the output Q is set to true
after the function block's first execution. After the
Function Block Execution
second execution, the output is false.
If the CLK input is initialized on, the R_TRIG output Q will be true for one function block instance
execution at a STOP Mode to RUN Mode transition after the first download, whether or not instance
memory is retentive.
Example
In the following example, when Input1 transitions from false to true, the coil, Detected, is set ON for
one function block execution. The output Q remains false until a new rising edge is detected.
GFK-2950C
February 2018
107
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