Back in the '80s, we used to do something similar that also took care of the reset pulse width. (See attached). The values of the C's and Rs set the reset pulse width and wtdog time.

We needed to have an ultra reliable system, but problem was that some power glitches could hang up processors. Wtdog counters could also get hung up - and we would see it happen with the early built-in uP wtdogs. Today they have the bugs out of it for the most part and if you have a good power supply and bypassing you won't have problems, yet stray alpha particles can still sometimes flip a bit.

While you can get away with it most of the time, be aware that you can sometime cause parts to draw a lot of current if the input isn't supposed to see analog.

You can get single gate schmitt triggers these days.

If you are having problems with your system hanging, most likely you have a ground path problem. Home run grounding with a beefy pavilion ground bus is the best way.



--------------------------------------------------------------------------------
Karl Schmidt                                  EMail [email protected]
Transtronics, Inc.                              WEB http://xtronics.com
3209 West 9th Street                             Ph (785) 841-3089
Lawrence, KS 66049                              FAX (785) 841-0434

Never put off till to-morrow what you
can do the day after to-morrow just as well. -- Mark Twain

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<<attachment: resetgen.png>>

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