From: Jason White <whitewaterssoftwareinfo@gmail.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Fri, 5 Jun 2020 03:48:53 -0700
Subject: Re: [EE] Detecting a change of level on four lines with digital
	logic/analog circuitry?
Thread-Topic: [EE] Detecting a change of level on four lines with digital
	logic/analog circuitry?
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Hello James,

This circuit is involved in area where safety could conceivably be
concerned. I've been asked to avoid programmable devices even if it is
bigger/worse/etc.

On Friday, June 5, 2020, James Burkart <james@burkartstudios.com> wrote:

> I'm curious. Why not microcontrollers?
> --
> Sincerely,
>
> James Burkart
> *925.667.7175*
>
>
> On Thu, Jun 4, 2020 at 2:37 PM Jason White <
> whitewaterssoftwareinfo@gmail.com> wrote:
>
> > Hi everyone,
> >
> > I have an application where I need to generate at pulse least 1
> microsecond
> > long any time a rising or falling edge is detected on four digital line=
s.
> > The four signals can change at any time to any direction. The pulse is
> used
> > to trigger a timer providing a reset signal to the rest of the system.
> > Microcontrollers and programmable logic devices aren't allowed.
> >
> > Four 74HC123s will do it, but are too big.
> > Four window comparators monitoring the signal through an RC will do it,
> but
> > also seems too big.
> >
> > Is four schmitt trigger XOR gates with four RC's the smallest
> > implementation?
> >
> > I was thinking some sort of analog implementation might be able to do i=
t
> > smaller. But AC coupling the four signals together would allow them to
> > cancel out. Perhaps a 4-bit encoder/decoder or multiplexer might do it
> > better?
> >
> > Regards,
> > Jason White
> > --
> > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
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Jason White
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