A function block groups an algorithm and a set of private data. It has inputs and outputs. - Falling pulse detection
Inputs
CLK : BOOL Boolean signal
Outputs
Q : BOOL TRUE when the input changes from TRUE to FALSE
Truth table
| CLK | CLK prev | Q |
|---|---|---|
|
0 |
0 |
0 |
|
0 |
1 |
1 |
|
1 |
0 |
0 |
|
1 |
1 |
0 |
Remarks
Although ]P[ and ]N[ contacts can be used in FFLD language, it is recommended to use declared instances of R_TRIG or F_TRIG function blocks in order to avoid contingencies during an Online Change.
ST Language
(* MyTrigger is declared as an instance of F_TRIG function block *)
MyTrigger (CLK);
Q := MyTrigger.Q;
FBD Language
FFLD Language
IL Language:
(* MyTrigger is declared as an instance of F_TRIG function block *)
Op1: CAL MyTrigger (CLK)
LD"Ladder diagram"
Ladder logic is a method of drawing electrical logic schematics. It is now a very popular graphical language for programming Programmable Logic Controllers (PLCs). It was originally invented to describe logic made from relays. The name is based on the observation that programs in this language resemble ladders, with two vertical "rails" and a series of horizontal "rungs" between them MyTrigger.Q
ST Q
See also
