Function block DIFU detects a rising edge from its input. This means that when there is a change of 0->1 at the input (input switch is closed) the output responds by a quick sequence of 0->1->0.

The output stays active (1) only for one execution time of the application (a fraction of a millisecond) and cannot be seen with CX Programmer or Syswin.

DIFU has one parameter which defines its target address.

DIFD is a corresponding function block for falling edge (1->0) detection.