AHA! So somebody else has seen something like this before.

I've got internal brownout enabled, and I am testing the POR bit at startup
and shutting the thing off if the startup was for any cause other than
power-on-reset.

However, There is no hardware brownoput reset.  Maybe that is going to be
needed.  Did you solve the problem on your 12C508?

--Lawrence

----- Original Message -----
From: "Bob Ammerman" <rammerman@adelphia.net>
To: "Lawrence Lile" <llile@toastmaster.com>
Sent: Monday, April 15, 2002 10:47 AM
Subject: Re: [PIC]: I've got the Sloooooooowwws


> Lawrence,
>
> I have noticed similar behaviour on a 12C508 which I attributed to
> incomplete recovery from a brownout condition, caused by bounce on the
power
> line. Note that after a brownout, according to mChip specs, anything goes.
>
> I did not have the ClkOut accessible, but I saw everything SLOW down.
>
> Bob Ammerman
> RAm Systems
>
> ----- Original Message -----
> From: "Lawrence Lile" <llile@toastmaster.com>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Monday, April 15, 2002 12:13 PM
> Subject: [PIC]: I've got the Sloooooooowwws
>
>
> > I've got an application that gets The Slows every once in a while.
What,
> > you may ask, are The Slows?
> >
> > The application is a timer for an appliance.  It is initiated when a
power
> > switch is closed on the appliance, runs at 4 Mhz with an RC oscillator,
> > using a 16F873 PIC.  15 times out of 16, the timer times out in, say, 40
> > seconds, and fires a relay which shuts off the power.  An LED blinks 1X
> per
> > second, and the frequency at the clockout pin is 1.15 MHz (within spec
for
> > the low tolerance resistor and capacitor I am using) Timeout is
determined
> > by counting up Timer1 interrupts, which are supposed to happen every
> 1/30th
> > second.
> >
> > One time in about 16, the timer times out not in 40 seconds, but in 3
> > minutes.  The blinking LED blinks at a very slow rate.  But a
measurement
> of
> > the clockout frequency is STILL 1.15 MHz.  I expected to find that the
> > oscillator was running real slow, but that doesn't seem to be the case.
> >
> > I am going to measure this again, because I don't believe my own test
> > results.
> >
> > There are two theories I am wondering about:  heat, and power.  This is
a
> > cooking appliance, it gets hot.  How hot?  I am going to thermocouple
the
> > PIC pretty soon and find out.  Second, the power is probably pretty
dirty
> on
> > startup.  There is a pair of contacts that close on a 1500 watt heating
> > element, also cranking up the power supply on the unit.  Big sparks and
> all.
> >
> > Could a PIC's oscillator start up at some wierd frequency if the power
was
> > dirty on startup, then stay there?  Could the oscillator run at some
wierd
> > frequency because it is hot?
> >
> > If I was on the other end of this post, I'd say The Slows are
impossible.
> > Since I just watched them, I can tell you they are.
> >
> >
> > -- Lawrence Lile
> > Sr. Project Engineer
> > Salton inc. Toastmaster Div.
> > 573-446-5661 Voice
> > 573-446-5676 Fax
> >
> > --
> > http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body
> >
> >
>

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