F_TRIGPLCopen motion icon

Function BlockClosedA 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 ChangeClosedApplies to downloading PLC code changes while the applicaiton is running..

ST Language

(* MyTrigger is declared as an instance of F_TRIG function block *)
MyTrigger (CLK);
Q := MyTrigger.Q;

FBD Language

F_Trig FBD

FFLD Language

F_Trig FFLD

IL Language:

(* MyTrigger is declared as an instance of F_TRIG function block *)
Op1: CAL MyTrigger (CLK)
LDClosed"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

R_TRIG