DF

Rising edge differential

DF is a rising edge differential instruction. The DF instruction executes and turns ON output o for a singular scan duration if the trigger i changes from an OFF to an ON state.

Parameters

Input

Unnamed input (BOOL)

Output

Unnamed output (BOOL)

Remarks

Be careful when programming with commands that effect the order in which a program is carried out, e.g. jump or loop instructions within a sequential function chart or a function block. The order of the instructions might change depending on the time when the instruction is carried out or the input value. Specific basic JUMP and LOOP instructions are: F19_SJP

Example

POU header

All input and output variables used for programming this function have been declared in the POU header. The same POU header is used for all programming languages.

	VAR
		Increment: BOOL:=FALSE;
		Counter: INT:=0;
	END_VAR

POU body

Each rising edge at the input Increment increments the counter.

LD body

BODY
    WORKSPACE
        NETWORK_LIST_TYPE := NWTYPELD ;
        ACTIVE_NETWORK := 0 ;
    END_WORKSPACE
    NET_WORK
        NETWORK_TYPE := NWTYPELD ;
        NETWORK_LABEL :=  ;
        NETWORK_TITLE :=  ;
        NETWORK_HEIGHT := 5 ;
        NETWORK_BODY
B(B_F,DF!,Instance,7,0,12,3,,?Di?Co);
B(B_VARIN,,Increment,5,1,7,3,);
B(B_F,E_ADD-2!,Instance,16,0,22,5,,?DEN?D?D?AENO?C);
B(B_VARIN,,Counter,14,2,16,4,);
B(B_VARIN,,1,14,3,16,5,);
B(B_VAROUT,,Counter,22,2,24,4,);
L(12,2,16,2);
L(1,0,1,5);
        END_NETWORK_BODY
    END_NET_WORK
END_BODY

ST body

IF DF(Increment) then
    Counter:=Counter+1;
END_IF;