Schmitt-Triggered Inputs (AN015)

Schmitt-triggering diminishes or eliminates logic-level uncertainty from signals having slow rise/fall times and those burdened with superimposed noise.

It achieves this using positive feedback to create a hysteresis band about the threshold of a logic input, which must be crossed in its entirety to effect a state change.
With the addition of external resistors, along with programmed positive feedback, the P8X32A can enjoy the benefits of Schmitt-triggering on any of its inputs.

Download the full PDF application note, and code samples.