The parameter assignments of the function block are effected by the determination of gain, the differentiator and the time constant lag, by which the output Y is delayed.

For very short sampling times and an input X unit step (input X jumps from 0 to 1.0), the output Y jumps to the value gain (in theory - in reality somewhat smaller, due to the sampling time not being infinitely small), and then returns to 0 with the delay time constant lag.