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'Oscillator Running?'
1999\01\07@224508 by cdupuy

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I have a 4mhz crystal attached to an 16f84 (pin 15 & 16).

I am having a problem picking up TMR0 interrupts.

Program appears to work fine in the simulator.

Is there a way to tell with only a DMM if the osc. is running?

1999\01\08@005410 by Michael J. Ghormley

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cdupuy wrote:
>
> I have a 4mhz crystal attached to an 16f84 (pin 15 & 16).
> I am having a problem picking up TMR0 interrupts.
> Program appears to work fine in the simulator.
> Is there a way to tell with only a DMM if the osc. is running?

I think that looking at OSC2/CLKOUT (pin 15) with a x10 probe is best.

Michael

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1999\01\08@055454 by Mark Willis

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Michael J. Ghormley wrote:
>
> cdupuy wrote:
> >
> > I have a 4mhz crystal attached to an 16f84 (pin 15 & 16).
> > I am having a problem picking up TMR0 interrupts.
> > Program appears to work fine in the simulator.
> > Is there a way to tell with only a DMM if the osc. is running?
>
> I think that looking at OSC2/CLKOUT (pin 15) with a x10 probe is best.
>
> Michael

 If you can connect a spare inverter (7404 or the like) on OSC2, use a
pullup of course if that's an OC inverter, you should be able to use
that as a buffer & read about Vcc/2 at the output (referenced to either
Vcc *or* ground), with just a DVM (I haven't tried this yet, but I've
planned to get to it.  It's sure worked in many logic circuits I've
worked with before!)  I assume a 50% duty cycle for OSC2, but IIRC
that's the right number <G>  A buffer or spare J-K flip flop or whatever
would work as well.

 Also a 4 MHz Shortwave receiver, or a frequency counter, if you have
one of those handy <G>

 Mark

 Keeping leads short between the PIC and the inverter's input here
would be a *good* idea, but I don't know of other problems than that

1999\01\08@062848 by paulb

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Michael J. Ghormley wrote:

> cdupuy wrote:
>> Is there a way to tell with only a DMM if the osc. is running?

> I think that looking at OSC2/CLKOUT (pin 15) with a x10 probe is best.

 Mmm, if you count a Fluke Scopemeter as a "DMM".

 Actually, you don't really want the DMM at all.  You want a LED
connected to one port (pin) with a 220 ohm resistor, and a test program
which generates a 1Hz flash on that port using no WDT, no interrupts,
just program loops.

 The program WL84.HEX might be of use.  See:
     http://www.dontronics.com/dt001cha.html#testing

 First rule; start simply.
--
 Cheers,
       Paul B.

1999\01\08@180408 by Regulus Berdin

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Hi,

I haven't tried this but it will maybe work.
Put a series capacitor on the OSC2 pin (about 100pf) and set your DMM to
AC voltage reading.  Most DMM's have high impedance input so this may
work.
If you got a voltage reading, the oscillator is working.

regards
Reggie

cdupuy wrote:
>
> I have a 4mhz crystal attached to an 16f84 (pin 15 & 16).
>
> I am having a problem picking up TMR0 interrupts.
>
> Program appears to work fine in the simulator.
>
> Is there a way to tell with only a DMM if the osc. is running?

1999\01\11@022915 by Dr. Imre Bartfai

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Hi,

have you grounded both pins with a 22 pF capacitor?

Imre


On Thu, 7 Jan 1999, cdupuy wrote:

> I have a 4mhz crystal attached to an 16f84 (pin 15 & 16).
>
> I am having a problem picking up TMR0 interrupts.
>
> Program appears to work fine in the simulator.
>
> Is there a way to tell with only a DMM if the osc. is running?
>
>

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