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Debouncer - The problem

Let's say you want to connect a switch to an FPGA.
You might build something like that:

But the problem with mechanical switches is that... they bounce!
When you press the push-button, you might get lucky and get something like that:

That's rare. More common are these...

FPGA counter

Now let's say you implement a counter inside your FPGA.
You add a display to see what's going on.

Power-on, things look good.

You press the push-button 10 times, and...

Not nice.