Re: ZIPGS 2-pin Crystal

[blackm00@cam.org (Michael Black)]

andrew.webber2@btinternet.com (Andrew Webber) wrote in message news:<6b297ed0.0206080046.3e7ea406@posting.google.com>...
> andrew.webber2@btinternet.com (Andrew Webber) wrote in message news:<6b297ed0.0205292353.68093fc8@posting.google.com>...
> > Hi,
> >
> > Quick question. I am trying to upgrade (Yes I have posted before ;-))
> > my ZIPGS and have read all the FAQs. The ZIPGS 8/16 I have is a 1.01
> > revision and has a soldered 2-pin crystal. There is a socket on the
> > card to accept a 4-pin TTL Oscillator, but this is currently empty. I
> > have also read the Hypercard stack.
> >
> > Now my question, can I just snip (suggested in the Stack) the 2-pin
> > crystal off the board and then plug in a standard 4-pin oscillator?
> >
> >
> > Thanks
> >
> > Andrew
>
> I recieved my 65c816-14 from WDC and replaced the old 65c816-7. All
> works find, but I still want to push the board above 8Mhz. Please :-)
> can anyone tell me if my ZIPGS will stop functioning if I snip the 2
> pin crystal (labeled x2) off the board and utilise the empty
> Oscillator (Labeld x1) socket with a 4-pin oscillator?
>
> The FAQ says there is extra curcuitry for for the 2-pin crystal
> (canister), so if I just snip it and put a 4-pin in is the board
> intellegent enough to know which one to use?
>
> Sorry if you are getting bored with my post....just to don't want to
> screw my working ZIPGS!
>
> Andrew

I don't know about that specific equipment.  But it wouldn't be
a matter of intelligence.

There'd be a gate somewhere, and both the input and output are brought
out so the crystal can be connected to their.  With the crystal there,
the gate acts as an oscillator.

But if the crystal isn't there, it's just a gate.  So a signal fed
to the pin that connects to the input pin of the gate would simply
be buffered by the gate, and then get into the rest of the circuit,
where it couldn't tell whether the gate was buffering or oscillating.

A lot of ICs are designed that way, so whether or not a piece of
equipment has the layout for an external oscillator, it often will
work.

If you have electronic background, it would be easy to take an ohmeter
of some kind, and see if one of the pins of the crystal connect to
the pin that is the output of the plug-in oscillator.  If that's the
case, one could be pretty certain that just clipping one  of the leads
of the crystal, and plugging in the oscillator would work.

   Michael