11/23 clock issue
tothwolf at concentric.net
Sat Feb 7 13:20:31 CST 2015
On Sat, 7 Feb 2015, Noel Chiappa wrote:
> > From: Tothwolf
> > Before I forget again, did you check for +5V on pin 1 (enable) when
> > you were testing your existing oscillator?
> Wow. Never thought to try that. Then again, I don't look for +5V on your
> average 74xxx when I'm debugging, either! :-) I mean, it's a trace, the
> solder on the pin looks good, that's as far as I go, usually! And
> there's nothing shown as connected to that pin on the circuit diagram.
> So I looked, and... it's at ground (or floating). The only pin that has
> anything is 14, at +5V (expected). But I looked online for some
> datasheets for similar oscillators, and some of them say 'pin 1 - N/C'.
> Are yours tri-state? (That's the enable pin on the tri-state ones.)
> I suppose even if yours are tri-state, I can still use them; a quick
> ohmmeter check shows that pin 1 isn't connected to either power or
> ground, so I can probably tie it high (via a resistor, which in addition
> to being normal practise, will prevent a major disaster in case I'm
> confused - a state I'm often in :-).
According to the datasheets, the parts I have use pin 1 as the enable pin,
so I assume they are. I've included links to the two datasheets in the
reply I sent you off-list. I usually just see pin 1 tied directly to 14 on
a lot of boards when these type of oscillators are used so I don't know
that you would even need a resistor there, just a mod wire would likely
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