F_TRIG block
Short summary
Name |
F_TRIG |
→POU type |
|
Category |
|
Conform to →IEC-standard |
behavior according to "Technical Report" (see below) |
Graphical interface |
|
Available since |
version 1.18.0 (for logi.CAD 3) |
Functionality
This block detects a falling edge.
→Turning input CLK off triggers output Q to return value TRUE (or an equivalent) from one execution of the function block to the next. Output Q returns value FALSE (or an equivalent) at the next execution .
Observe:
If the input CLK is connected to value FALSE, output Q returns FALSE from its first execution onward following a →cold restart. This behavior has been implemented according to Technical Report IEC TR 61131-8 (Programmable controllers – Part 8: Guidelines for the application and implementation of programming languages).
In-/outputs
|
Identifier |
Description |
|
Inputs: |
CLK |
BOOL |
current value |
Outputs: |
Q |
BOOL |
flag showing falling edge detection |
Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.
See:
"Blocks for safe logic" whether this block is supported for developing safety-relevant applications.
"Highlighting safe logic in the FBD-editor" for the effects when using the block as a block for safe logic .
Example for usage within ST-editor
PROGRAM Test
VAR
Activator : F_TRIG;
Out : BOOL;
Trigger : BOOL;
END_VAR
Activator(CLK := Trigger, Q => Out);
(* Instance of block 'F_TRIG' is called. *)
(* Input 'CLK' gets value from 'Trigger' variable. *)
(* Output 'Q' returns TRUE for one cycle, if 'Trigger' was set to FALSE. *)
(* Variable 'Out' accesses the output 'Q'. *)
END_PROGRAM
When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.