5 Feb
2015
5 Feb
'15
11:44 p.m.
Noel Chiappa wrote:
Hmm, may be since his hints are standard debugging technique and you aren't
really familiar with debugging??
You don't ned no pullup for +5. All open TTL inputs are reading High w/o
any pullup.
Regards,
Holm
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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!?!?' :-)
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.
Noel