R_TRIG

VAR_INPUT

VAR_INPUT
    CLK     : BOOL; (* Signal to detect *)
END_VAR

VAR_OUTPUT

VAR_OUTPUT
    Q       : BOOL; (* Edge detected *)
END_VAR
VAR
    M       : BOOL; 
END_VAR

The output Q and the help variable M will remain FALSE if the input variable CLK is FALSE. As soon as CLK returns TRUE, Q will first return TRUE, then M will be set to TRUE. This means each time the function is called up, Q will return FALSE until CLK has falling edge followed by an rising edge.

Requirements