R_TRIG

Rising edge detector. Output Q is TRUE for one scan cycle when the input CLK transitions from FALSE to TRUE.

IEC 61131-3	Section 2.5.2.3.2
Support	Supported

Inputs

Name	Type	Description
CLK	BOOL	Signal to monitor for rising edge

Outputs

Name	Type	Description
Q	BOOL	Edge output (TRUE for one scan on rising edge)

Behavior

The function block stores the previous value of CLK. When CLK transitions from FALSE to TRUE, the output Q is set to TRUE for one scan cycle. On all subsequent scans where CLK remains TRUE, Q is FALSE. When CLK is FALSE, Q is always FALSE.

Example

This example detects a rising edge. The input starts TRUE, so Q is TRUE on the first scan (transition from the default FALSE to TRUE).

Try it

Source

PROGRAM main
   VAR
      edge1 : R_TRIG;
      detected : BOOL;
   END_VAR

   edge1(CLK := TRUE, Q => detected);
   (* detected is TRUE on the first scan because CLK rose from FALSE to TRUE *)
END_PROGRAM

See Also

• F_TRIG — falling edge detector