R_TRIG / R_TRIG_S - Rising edge detector

This edge detection function block detects a rising edge. If a rising edge is detected at the input CLK, the output Q changes from FALSE to TRUE. Q remains TRUE for one execution of the function block. If the function block is called for the first time, Q is FALSE until the first rising edge is detected.

The function block is available as standard function block R_TRIG and safety-related function block R_TRIG_S.

R_TRIG

Parameter	Data types	Description
CLK	BOOL	Detects a rising edge
Q	BOOL	If a rising edge is detected, Q changes from FALSE to TRUE

R_TRIG_S

Parameter	Data types	Description
CLK	SAFEBOOL	Detects a rising edge
Q	SAFEBOOL	If a rising edge is detected, Q changes from FALSE to TRUE

NOTE:

Function blocks have to be instantiated. Like variables, instances have to be declared before they can be inserted in a code body. Instances must be unique within the POU. In the following example, the instance name 'R_TRIG_S_1' is used for the R_TRIG_S FB.

Example for a safety-related function block declaration R_TRIG_S

Variables declarations in this example

NOTE:

If you want to use the standard function block R_TRIG in your code worksheet, you have to select the data type 'R_TRIG' for the function block instance in the local variables worksheet. Accordingly, the data type 'BOOL' must be used instead of 'SAFEBOOL'.