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'[PIC]: Maximum frequency specs for pic inputs'
2002\09\19@142218 by Vis Naicker

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>> Mike Singer PICs could serve as counters up to 50 Mhz.
You could tristate outputs configuring them
as inputs, when values are "1", for example.
<<     Were I to embark on making a frequency counter using
just a PIC ( minumim of external components , prescaler
optional ) which PIC would be the most appropraite ?

I think that the 16Cxx parts were pushed to 50MHz + ,
but can the Flash parts perform as well ? Where can I
find this kind of information ? Not the datasheet ...
Electrical specifications are not entirely clear .

And (  ;-)  ) I don't want exactly the manufacturer's spec's ; I want to know what can I push for in the real
world ? Results of frequcnecy achieved may vary amongst PIC's from the same batch etc regardless ? Push it to the
Max , let me get burned .

Vis Naicker

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2002\09\19@145349 by Olin Lathrop

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> I think that the 16Cxx parts were pushed to 50MHz + ,
> but can the Flash parts perform as well ? Where can I
> find this kind of information ? Not the datasheet ...

Um, why not?  I'm pretty sure there is a max timer 1 input frequency spec in
there somewhere.

> Electrical specifications are not entirely clear .

What part of "maximum frequency = xxx" is unclear?  Try asking a more
specific question.

> And (  ;-)  ) I don't want exactly the manufacturer's
> spec's ; I want to know what can I push for in the real
> world ?

Let's not waste time on this nonsense.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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2002\09\19@163631 by mpoulton

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---- Original message ----
>Date: Thu, 19 Sep 2002 14:52:44 -0400
>From: Olin Lathrop <spam_OUTolin_piclistTakeThisOuTspamEMBEDINC.COM>
>Subject: Re: [PIC]: Maximum frequency specs for pic inputs
>To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
>
>> I think that the 16Cxx parts were pushed to 50MHz + ,
>> but can the Flash parts perform as well ? Where can I
>> find this kind of information ? Not the datasheet ...
>
>Um, why not?  I'm pretty sure there is a max timer 1 input
frequency spec in
>there somewhere.

See below.

>> Electrical specifications are not entirely clear .
>
>What part of "maximum frequency = xxx" is unclear?  Try
asking a more
>specific question.

The specs is clear, but meaningless in this context.  How
was the spec determined?  What is the reliability of a part
at that frequency?  What is the reliability at 25% above
that frequency?  What is the failure mode if pushed too fast?

>> And (  ;-)  ) I don't want exactly the manufacturer's
>> spec's ; I want to know what can I push for in the real
>> world ?
>
>Let's not waste time on this nonsense.

How is that nonsense?  We all know that parts are
consistenly under- or over-spec'ed by the manufacturer.
Sometimes the data sheet gives wildly
optimistic "information", while other times the "absolute
maximum ratings" are far below the real limits.  You can
guarantee that a PIC spec'ed for 20MHz max will work at 21.
It might even work fine at 25, 30, or more.  At some point,
it will become unreliable.  He wants speed vs. reliability
information for clock speeds beyond those Microchip designed
for.
--
Mike P.
MTP Technologies
KC0LLX

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2002\09\19@173709 by Dale Botkin

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On Thu, 19 Sep 2002, Mike P. wrote:

> The specs is clear, but meaningless in this context.  How
> was the spec determined?  What is the reliability of a part
> at that frequency?

Guaranteed 100.0%, over the full operational range.

> What is the reliability at 25% above
> that frequency?

Somewhere between 0.0% and 100.0%, depending on moon phases, orientation
of dead fish, whatever.  Olin's very valid point is, since it's not tested
or guaranted, you don't know.  If you want to know you'll have to
individually test each chip to whatever your specifications might be,
including the full range of possible temperatures, power supply ranges,
etc.  And of course you won't know how it will work over time.

> What is the failure mode if pushed too fast?

See above.

> >Let's not waste time on this nonsense.
>
> How is that nonsense?  We all know that parts are
> consistenly under- or over-spec'ed by the manufacturer.

Under-spec under certain conditions, probably yes.  But bear in mind that
the published specs are what Microchip will guarantee over the full range
of temperature, voltage, ripple, capacitive load, vibration, etc.

> You can guarantee that a PIC spec'ed for 20MHz max will work at 21.

No, you can't.  I'd bet a few bucks on it for a hobby project, but I'd
never guarantee it, and neither will Microchip.  Again, you'd have to test
each unit individually to know for sure.  After you've tested X number you
can say with some degree of confidence what they'll do, but the next die
shrink or even the next production lot can completely invalidate your
findings.

> It might even work fine at 25, 30, or more.  At some point,
> it will become unreliable.  He wants speed vs. reliability
> information for clock speeds beyond those Microchip designed
> for.

Then he's going to have to get it the hard way, once chip at a time,
because it simply doesn't exist.  Of course you're welcome to prove me
wrong by coming up with any instance where someone has guaranteed,
documented over-spec numbers, but this has been discussed to death
numerous times.  So far I don't think anyone's come up with any.

Dale

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2002\09\19@175250 by Bob Blick

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On Thu, 19 Sep 2002, Dale Botkin wrote:
> > You can guarantee that a PIC spec'ed for 20MHz max will work at 21.
>
> No, you can't.  I'd bet a few bucks on it for a hobby project, but I'd
> never guarantee it, and neither will Microchip.  Again, you'd have to test
> each unit individually to know for sure.  After you've tested X number you
> can say with some degree of confidence what they'll do, but the next die
> shrink or even the next production lot can completely invalidate your
> findings.

Actually, there are companies that will guarantee it. Connectix used a 20
MHz PIC in the parallel port Quickcam running at 24 MHz. They did it for a
few years with OTP parts over many production lots.

This is a topic that continues to surface, and is off the exact beginning
of this thread, which was the 50MHz spec of the TMR0 external clock input.
I don't know anyone who has tested that spec. Personally I suspect it
won't do too much better than the rated spec.

Cheerful regards,

Bob

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2002\09\19@175603 by mpoulton

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---- Original message ----
>Date: Thu, 19 Sep 2002 16:36:29 -0500
>From: Dale Botkin <dalespamKILLspamBOTKIN.ORG>
>Subject: Re: [PIC]: Maximum frequency specs for pic inputs
>To: .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
<snip>
>>He wants speed vs. reliability
>> information for clock speeds beyond those Microchip
>>designed for.
>
>Then he's going to have to get it the hard way, once chip
at a time,
>because it simply doesn't exist.  Of course you're welcome
to prove me
>wrong by coming up with any instance where someone has
guaranteed,
>documented over-spec numbers, but this has been discussed
to death
>numerous times.  So far I don't think anyone's come up with
>any.

I got the impression he was looking for personal experiences
of people on the list, not numbers from Microchip.  Of
course MC's not going to say anything about it -- if they
were, they would have put it in the data sheet.  I would
imagine that, amongst the vast readership of this list,
there are at least a few people who have overclocked some
PIC's.  I think he wants to hear from them.
--
Mike P.
MTP Technologies
KC0LLX

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2002\09\19@234342 by Mike Singer

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Bob Blick wrote:
.
> This is a topic that continues to surface, and is off the
> exact beginning of this thread, which was the 50MHz
> spec of the TMR0 external clock input. I don't know
> anyone who has tested that spec. Personally I suspect it
> won't do too much better than the rated spec.
>

From AN592 (00592d.pdf) :
Frequency Counter Using PIC16C5X:
- Frequency range   50MHz - 10 MHz
- Precise "gate" delay   1ms
- Resolution 10 KHz

Mike.

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2002\09\20@005240 by Dale Botkin

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On Thu, 19 Sep 2002, Bob Blick wrote:

> On Thu, 19 Sep 2002, Dale Botkin wrote:
> > > You can guarantee that a PIC spec'ed for 20MHz max will work at 21.
> >
> > No, you can't.  I'd bet a few bucks on it for a hobby project, but I'd
>
> Actually, there are companies that will guarantee it. Connectix used a 20
> MHz PIC in the parallel port Quickcam running at 24 MHz. They did it for a
> few years with OTP parts over many production lots.

Yes, but my point is that either **THEY** did the characterization,
testing, and took full responsibility, or they cut a special deal with
Microchip.  If YOU OR I run a 20MHz part at 24MHz, nobody's guaranteeing
it will work (unless you want to).

> This is a topic that continues to surface, and is off the exact beginning
> of this thread, which was the 50MHz spec of the TMR0 external clock input.
> I don't know anyone who has tested that spec. Personally I suspect it
> won't do too much better than the rated spec.

I agree with you.

Dale

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2002\09\20@021826 by Peter L. Peres

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On Thu, 19 Sep 2002, Olin Lathrop wrote:

*>> I think that the 16Cxx parts were pushed to 50MHz + ,
*>> but can the Flash parts perform as well ? Where can I
*>> find this kind of information ? Not the datasheet ...
*>
*>Um, why not?  I'm pretty sure there is a max timer 1 input frequency spec in
*>there somewhere.

No but there is a minimum pulse width which amounts to the same thing. The
16C54(A) specced 20ns (50MHz) but 16F84A has 50ns I think. I built several
counters (most for PLL purposes, others with display, from 16 to 40 bits
resolution). I never used one beyond 20MHz (did not need it), neither with
16C54 nor with 16F84. I did use one for UHF using a prescaler but that put
the counter input frequency under 10MHz.

Peter

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2002\09\20@062540 by Michael Rigby-Jones

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> -----Original Message-----
> From: Mike P. [SMTP:EraseMEmpoultonspam_OUTspamTakeThisOuTmtptech.com]
> Sent: Thursday, September 19, 2002 10:55 PM
> To:   PICLISTspamspam_OUTMITVMA.MIT.EDU
> Subject:      Re: [PIC]: Maximum frequency specs for pic inputs
> I got the impression he was looking for personal experiences
> of people on the list, not numbers from Microchip.  Of
> course MC's not going to say anything about it -- if they
> were, they would have put it in the data sheet.  I would
> imagine that, amongst the vast readership of this list,
> there are at least a few people who have overclocked some
> PIC's.  I think he wants to hear from them.
>
The responses you have been given so far are typical of professional
engineers.  They want to make products that are absolutely 100% reliable,
and to do that you do not exceed the manufacturers specifications.

As a purely "for interest" exercise then fine.  If you take a look at the
archives I'm pretty sure that someone did post the results of "overclocking"
a PIC some time ago (sorry, can't give a specific date, but over a year
ago).  ISTR that they managed something over 30MHz from a 20MHz part.  You
have to consider the implications of running the PIC this fast however.
Timing issues, especially involving RMW problems will cause you no end of
grief and are likely to be voltage/temperature sensitive.

Regards

Mike

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2002\09\20@073654 by Kevin Blain

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As a purely for interest exercise, whilst at my last company, I played
with overclocking.

I was developing a device which inserted a pattern overlayed onto a
video signal, to indicate low battery in the video transitter.

Being an RF company, I was using an RF signal generator as an osc source
for the PIC at the time, and was running a 4MHz PIC 16F873.

I managed to get the thing going up at around 40MHz.

Interestingly, there were some gaps in the coverage. At about 24MHz, it
stopped, then picked upagain at around 26MHz, then there were a few more
gaps up the range.

The PIC was generating a flashing logo with the letters 'LB' in, and I
was able to get a fairly high resolution before the PIC gave up!


Regards, Kevin

> {Original Message removed}

2002\09\21@030743 by Michael Rigby-Jones

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{Quote hidden}

That seems odd.  Perhaps standing waves in the cable bewteen signal
generator and PIC, bearing in mind the PIC's OSC pin will not have a 50Ohm
input impedance?

Regards

Mike

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2002\09\23@171605 by Vis Naicker

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Oops , I think I have seen this thread before ....
I am not interested in overclocking the damn thing.
I don't see a freq past the manufactures specs to
a prescaler as overclocking , just want to know what has been achieved by hobbyists who have done
this previously.
But I repeat myself . I think I did ask a simple clear question , Oilyn.
Perhaps I out to rephrased the Subject tag as
Microchips freq spec's for C vs (1) F part vs (11) REAL WORLD


On a OT - financial strain has meant that I should be
offline for an indefinite period , so I should have
at least 80 min/day more for the REAL WORLD .
No more PICLIST and some other few lists.

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