I am trying to build a 6502 computer, and I am making a bootleg keyboard for the 6502 using push buttons. I don't want more than one button to be pushed at once so I need help building circuitry that drops current if two buttons are pressed., I know this is probably really simple, but im a noob

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JMP $FFD2

You can put diodes in series with the buttons so one output line can't fight another one. Another way around it is that in the scanning, you only let one of the output bits be active at a time, and the others are high-impedance while the active one is pulling down. It has the effect of being like an open-collector output, and the only pull-ups are passive. There's no excess current that way. You might have outputs feeding the rows and inputs reading the columns, or vice-versa.

There are some keyboard and keypad ideas in the keypads and keyboards section of the potpourri page of the 6502 primer.

You'll want to pay attention to debouncing. Do it in software to make it easier.

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

its only going to be a hex keyboard with some command buttons, but if you could suggest one of the matrx keyboards id be more than happy to try them

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JMP $FFD2

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

A couple that look good are these two at Jameco:
http://www.jameco.com/webapp/wcs/stores ... _196171_-1 (2x8)
http://www.jameco.com/webapp/wcs/stores ... _152063_-1 (4x4)


I have used, and like, the Grayhill 87 type. They take .5" square per key, and can be stacked into whatever dimensions you want, all soldered into standard prototyping board with holes on .1" centers. They have transparent key caps that you can put your own labled under. I used them in this keypad shown in the potpourri page of the 6502 primer:



and in the automated test equipment:



Grayhill's .pdf page on it is at http://www.grayhill.com/assets/1/7/Keypads_87.pdf

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!