11/23 clock issue
holm at freibergnet.de
Fri Feb 6 01:44:05 CST 2015
Noel Chiappa wrote:
> > From: Brent Hilpert
> > Well, try removing W1 to isolate the output of the xtal oscillator E15
> > from inverter input pin E4.4.
> Thanks! Too late to try it today, but first thing tomorrow..
> It seems like every time you answer one of my queries, I smack my forehead
> and say 'That's an excellent idea! Why didn't _I_ think of that!?!?' :-)
Hmm, may be since his hints are standard debugging technique and you aren't
really familiar with debugging??
> > If you're not familiar with them, E15 is an integrated xtal oscillator,
> > not just a crystal - the crystal and oscillator logic are both in that
> > can
> I'm not familiar, so thanks for the tip. Wonder where I'll find one if that's
> what's bad... :-)
> > Could also (with W1 removed) pull E4.4 hi/lo while watching the
> > inverter output E4.16 to see if it responds correctly with the
> > inversion.
> Since it's a tri-state, I may need to hit the enable somehow. Oh, wait, I
> see, it's hard-wired on via a pull-down. (I wonder why they needed a
> pull-down? And I wonder what the test point is there for?) And I guess I need
> like a 5K series pull-up resistor to +5, right? (Ground I can just tie
> directly, right?)
> Anyway, thanks again for the help - very, very useful.
You don't ned no pullup for +5. All open TTL inputs are reading High w/o
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