F_EDGE (Attribute)

F_EDGE is an attribute that can be used on the BOOL variables that are declared in a VAR_INPUT section. By using this attribute, the variable it is used on will only be TRUE when there is a falling edge detected on the input value.

Please also have a look at R_EDGE for a rising edge attribute.

All variables with the F_EDGE attribute will only be updated when BEGIN or UPDATEIO() is executed.

Example:

For an example of the R_EDGE (which is similar to F_EDGE), please have a look at the CTD function block.