Lenze DDS v2.3 - Manual (Page 305)

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IEC 61131-3 Standard functions
14-13
l
DDS EN 2.3
14.5.2 F_TRIG
Falling edge detector
FUNCTION_BLOCK F_TRIG
VAR_INPUT
CLK : BOOL;
END_VAR
VAR_OUTPUT
Q : BOOL;
END_VAR
VAR
M : BOOL := TRUE;
END_VAR
Q := NOT CLK AND NOT M;
M := NOT CLK;
END_FUNCTION_BLOCK
As long as the input variable CLK returns TRUE,
the output Q and the auxiliary variable M will be FALSE.
As soon as S1 is FALSE, Q will first return TRUE and then M will be switched to TRUE.
I.e.: with every subsequent function call,
Q
will return FALSE until CLK has a rising and another falling edge.
Examples
Declaration:
FTRIGInst : F_TRIG;
IL FBD
CAL FTRIGInst(CLK:=VarBOOL1)
LD FTRIGInst.Q
ST VarBOOL2
ST
FTRIGInst(CLK:=VarBOOL1);
VarBOOL2:=FTRIGInst.Q;
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