[sdiy] gates and clock inputs to a microprocessor

[Chris Muir]

I went with the conservative approach on a recent module:
- comparator on input (339)
- voltage follower with gain on output. I needed 10 V gates  
(optionally 15 V), you could get away with just a voltage follower if  
you only need 5 V gates.

- C

On Oct 25, 2009, at 11:36 AM, Danjel van Tijn wrote:

> I am working on module where I have a microprocessor receive gate/trig
> inputs for clock and reset controls.
>
> what do I need in terms of analog circuits to condition those inputs?
> e.g.
> -for input over voltage protection would I use a resistor plus 5V  
> zener?
> -comparator to allow low voltage signals trigger?
> -series diode to protect from negative voltage?
>
> Also the uP will be outputting gate signals. Should these be buffered
> or can I just drive straight from the output pins?  (it is an
> atmega168)
>
> Also if the input pins of the microprocess are using pullups, how
> would I have an incoming pulse trigger on rising edge? would I need to
> put it through an inverter?
>
> I am sure all this stuff has been covered and well documented in
> schematics. I am going to head over to MFOS to get some ideas but
> thought it would be good to check some other resources.
>
>
> cheers,
> Danjel
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Chris Muir
cbm at well.com	
http://www.xfade.com