Re: IIgs frozen in time!

[Tristan Mumford <xtristan.xmumford@xgmail.xcom>]

David Wilson wrote:

> On Sep 22, 10:15 am, Tristan Mumford <xtristan.xmumf...@xgmail.xcom>
> wrote:
>> My main suspect is the clock xtal. Testing it is the biggest issue I
>> have. I think I can get away with injecting a clock signal into the XIN
>> pin of the clock chip briefly to see of the clock advances. Would this be
>> destructive?
> 
> I personally would not try feeding a signal into the XIN pin. Crystal
> oscillator circuits would (I think) be fairly sensitive.

They seem to be fairly robust. The problem is the X factor of voltage. I
have driven an xtal circuit with a clock before. But there were no unknowns
that time. I knew how the IC worked. This one is a little black box.

> 
> Can you borrow a CRO? 
Lamentably no. It has been a source of immense irritation for many years.

> I hooked up mine to the IIgs clock chip and got 
> a lovely sine wave on one of the XIN/XOUT pins (the other was a
> slightly lumpy sine wave).

That makes me happy to hear.

> 
> With the IIgs off the 1Hz pin was not active.

True. If you feel the need to probe the clock with a CRO again could you
please tell me if at all possible the relationship between the 1Hz line and
the enable pin? Or actually the enable pin and data pin would be good to
know. Basically I just want to know whether its active high or low.

Remember I haven't really ruled out the support chips either. For all I know
the clock could be paralysed by an external force.

Thanks for the probing by the way!

Tristan.

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