Is it possible to have an input, say a button, that does one positive edge clock pulse? So I want to press this button once and it does a 0->1->0. I can't think of anyway to do it because it changes twice with one input.

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    \$\begingroup\$ fyi: A switch can generate a burst of edges, if you consider contact bouncing. \$\endgroup\$ – Nick Alexeev Feb 24 '16 at 2:00
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    \$\begingroup\$ Please explain very clearly how you want to press the button and what you want the output to be. For example, do you press and hold the button forever, or do you press it and release it? And do you want the output to be a rising edge only, or rise followed by fall? \$\endgroup\$ – mkeith Feb 24 '16 at 5:33

A single clean pulse can be created using a latch circuit, (cross coupled gates). Ideally this works best with a switch or push button having a SPDT format.

Another option is to use a SPST switch with (debounce) filtering which is basically an RC filter followed by a Schmitt trigger circuit.

One more idea is a one shot circuit using a chip such as a 555 series timer. With a 555 design you can even set up the desired pulse width.

Here is a Google link showing several of the above mentioned designs:

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