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'Overclocking a PIC16F84'
2000\05\02@031205 by Werner Soekoe

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Hi

I need to run a PIC16F84 on 4.194304 MHz (2^22 hz) for some precision
timing, and since this clock speed is a multiple of 1024, it works extremely
well with the Timer0 module on the PIC. Question is, would it hurt to run a
4Mhz PIC at this speed, or should I rather opt for a 10Mhz PIC?

Regards,
Werner Soekoe
Information Systems Manager
Free State Legislature
spam_OUTwernersTakeThisOuTspamfsl.gov.za
Tel. (051) 407-1109
Fax. (051) 407-1137
Cell. 082 376 8383
Country Code. +27

2000\05\02@034102 by Joe Colquitt

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>
> I need to run a PIC16F84 on 4.194304 MHz (2^22 hz) for some precision
> timing, and since this clock speed is a multiple of 1024, it works
> extremely well with the Timer0 module on the PIC. Question is, would it
> hurt to run a 4Mhz PIC at this speed, or should I rather opt for a 10Mhz
> PIC?

All F84's come off the same wafer and are tested for speed performance.
An -04 is one that doesn't meet -10 specs, it may even run at 9.5MHz,
but not 10MHz. I've an -04 that's quite happy at 7.3MHz. You can't
GUARANTEE that an -04 will run at 4.2MHz but it probably will. If this
is a one-off I'd say try it but for a production run you'd be safer
using -10 devices, unless you want to test each -04 as it goes into
service. Most of them would pass I think, the 4.2MHz being so close to
the nominal 4MHz grading. In a sense you aren't overclocking, the -04's
just have a possible operating range of 4 to 10 MHz.

2000\05\02@035602 by Andrew Warren

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Werner Soekoe <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU> wrote:

> I need to run a PIC16F84 on 4.194304 MHz .... would it hurt to run
> a 4Mhz PIC at this speed, or should I rather opt for a 10Mhz PIC?

Werner:

All 16F84s are manufactured using the same die and the same process;
the only thing that makes a -10 part different from a -4 part is that
the -10 part has been TESTED (and passed) at 10 MHz.

Microchip doesn't publicize any data on the number of chips that fail
at 10 MHz but pass at 4, but the general feeling out here in the
world is that the number must be very small.  Many of us have played
with PICs at high speeds; at room temperature, I got a PIC16C54-XT
(the old name for the PIC16C54-04) to run at 45 MHz.  It's EXTREMELY
unlikely that a -4 part will fail at 4.194304 MHz; in fact, it's
unlikely that it'll even exhibit ANY behavior outside of Microchip's
published specs for the part.

However... If you're going into large-scale production of your
product, or if it's important that the PIC meet ALL of its published
specs (current draw and temperature-range, particularly), then you
should use a -10 part; if you use a -4, you won't have any recourse
with Microchip should it fail.

-Andy


=== Andrew Warren - fastfwdspamKILLspamix.netcom.com
=== Fast Forward Engineering - San Diego, California
=== http://www.geocities.com/SiliconValley/2499

2000\05\02@035827 by Andrew Warren

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Joe Colquitt <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU> wrote:

> All F84's come off the same wafer and are tested for speed
> performance. An -04 is one that doesn't meet -10 specs, it may even
> run at 9.5MHz, but not 10MHz.

   Um, no.  It's a small disctinction, but an important one:  A -10
   part DOES meet the -10 specs, but a -04 doesn't necessarily FAIL
   to meet them.

   -Andy


=== Andrew Warren - EraseMEfastfwdspam_OUTspamTakeThisOuTix.netcom.com
=== Fast Forward Engineering - San Diego, California
=== http://www.geocities.com/SiliconValley/2499

2000\05\02@075455 by Jinx

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Sorry to be pedantic now that the original question has been answered, but
having trouble understanding "doesn't necessarily fail".

"doesn't necessarily" implies that there is some flexibility with regard
to the consigning of parts to the -04 grade.

Is there not an absolute limit to exclude parts ? I realise that guaranteed
perfomance is important (perhaps my example of 9.5/10 was not a good
one) but a part that meets -10 specs should be a -10 part. What reason
would there be to reject it ?


From: Andrew Warren <fastfwdspamspam_OUTIX.NETCOM.COM>
{Quote hidden}

2000\05\02@090610 by Dale Botkin

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On Tue, 2 May 2000, Jinx wrote:

> Sorry to be pedantic now that the original question has been answered, but
> having trouble understanding "doesn't necessarily fail".
>
> "doesn't necessarily" implies that there is some flexibility with regard
> to the consigning of parts to the -04 grade.
>
> Is there not an absolute limit to exclude parts ? I realise that guaranteed
> perfomance is important (perhaps my example of 9.5/10 was not a good
> one) but a part that meets -10 specs should be a -10 part. What reason
> would there be to reject it ?

Since there's a price difference, there will be a difference in demand.
This means you, as a manufacturer, only need X number of 10MHz parts. Once
you've tested and verified X (or even 2X) you just don't need any more.
If 100% of your stock meets 10MHz specs, and you make them all -10 parts,
then there's a shortage of -04 parts.

Dale
---
The most exciting phrase to hear in science, the one that heralds new
discoveries, is not "Eureka!" (I found it!) but "That's funny ..."
               -- Isaac Asimov

2000\05\02@115255 by Lea

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At 07:39 PM 5/2/00 +1200, you wrote:
> I need to run a PIC16F84 on 4.194304 MHz (2^22 hz) for some precision
> timing, and since this clock speed is a multiple of 1024, it works
> extremely well with the Timer0 module on the PIC. Question is, would it
> hurt to run a 4Mhz PIC at this speed, or should I rather opt for a 10Mhz
> PIC?

Hi!, I have a F84 runing at 10 Mhz, it's a -04 part because here in my
country is almost impossible to find a -10 part, I've been tested it between
5 - 60 C temperature and it was Ok.
It's working actually as a packet transmitter only (it broadcast telemetry,
a cheaper version of a pager jeje), and still working 2 months ago, so...
don't worry, a couple of mhz more than the specified will not harm it at all!.

But keep in mind that what I am doing could be unstable, taking it to the
limit, It works and pass my tests but in a serious commercial aplication
would be better use -10 part.

so IMHO for 2 o 3 Mhz more, -10 part will not be necessary.

see you.
  Leandro J. Laporta (LU2AOQ)     mail: @spam@lu2aoqKILLspamspamyahoo.com
wrk: Arg. Assoc. for Space Tech.   ham: TCP/IP high speed group HSG


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2000\05\02@122409 by Andrew Warren

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Jinx <KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU> wrote:

> > > All F84's come off the same wafer and are tested for speed
> > > performance. An -04 is one that doesn't meet -10 specs, it may
> > > even run at 9.5MHz, but not 10MHz.
> >
> > Um, no.  It's a small disctinction, but an important one:  A -10
> > part DOES meet the -10 specs, but a -04 doesn't necessarily FAIL
> > to meet them.
>
> a part that meets -10 specs should be a -10 part. What reason would
> there be to reject it ?

Jinx:

The reason's simple:  If Microchip tested all parts at 4 and 10 MHz,
then labeled each according to the highest-speed spec it met, they'd
have warehouses full of unwanted -10s while -04s would be back-
ordered for years.

-Andy


=== Andrew Warren - RemoveMEfastfwdTakeThisOuTspamix.netcom.com
=== Fast Forward Engineering - San Diego, California
=== http://www.geocities.com/SiliconValley/2499

2000\05\02@154810 by Henrik Nielsen

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Hi
I have 400 pic 16F84 04 running at 8 mhz, non of them has fail
in 6 monts running 24 hour a day
they are running a simple code with text on a video signal no problem

Regards
   spamBeGonehenrikspamBeGonespamicelektro.dk

{Original Message removed}

2000\05\02@183935 by Tony Nixon

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Werner Soekoe wrote:
>
> Hi
>
> I need to run a PIC16F84 on 4.194304 MHz (2^22 hz) for some precision
> timing, and since this clock speed is a multiple of 1024, it works extremely
> well with the Timer0 module on the PIC. Question is, would it hurt to run a
> 4Mhz PIC at this speed, or should I rather opt for a 10Mhz PIC?
>

I wouldn't be too fussed about using a 4MHz part.

--
Best regards

Tony

http://www.picnpoke.com
TakeThisOuTsalesEraseMEspamspam_OUTpicnpoke.com

2000\05\02@192904 by David VanHorn

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At 09:54 PM 5/2/00 +0200, Henrik Nielsen wrote:
>Hi
>I have 400 pic 16F84 04 running at 8 mhz, non of them has fail
>in 6 monts running 24 hour a day
>they are running a simple code with text on a video signal no problem


When you can get a written variance from microchip to use them at 10, then
call me.

- --
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http://www.spamwhack.com  A pre-emptive strike against spam!

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2000\05\06@100715 by Marc

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> Is there not an absolute limit to exclude parts ? I realise that guaranteed
> perfomance is important (perhaps my example of 9.5/10 was not a good
> one) but a part that meets -10 specs should be a -10 part. What reason
> would there be to reject it ?

Test cost.  A distinction between 10MHz, 4MHz, and "bad chip" requires 2 tests.
A distinction between either one of 10 or 4 MHz, versus "bad chip" can be
done with only 1 test.

A 4MHz part is seldomly a part that has failed a 10MHz test earlier, but most
probably is a part that has been tested at 4MHz only - because the 4MHz stock
was low and needed refilling.

Whether the part runs OK at 10MHz or not is not known.  You can screen the
parts yourself if you want to select "good" from "bad" chips.

2000\05\06@101331 by Rich Clemens

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>From my days of production lines is it perhaps the "process" is in tight
control and testing steps up to 10MHz otherwise the "normal" is 4MHz?
--




{Original Message removed}

2000\05\08@112835 by Don Hyde

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I had a nice discussion about clocks and other specs with a Microchip FAE,
and what he said seemed really reasonable.  Basically, the specs state what
Microchip guarantees and is willing to stand behind.  Once you buy the
chips, you're free to do whatever you want with them, but if what you're
doing is outside of the specs, don't expect Microchip to back you up.  Any
guarantees you offer will be strictly your own.

The kicker with most of the specs is "over the specified temperature range".
At room temperature, just about any chip will perform far beyond its
specifications.  If you are certain your chips will always be at exactly
25C, then you can run them way beyond the specs.

This same FAE said he had a customer who was having good luck running some
at 10 times the spec'ed clock rate in a certain application.  The customer
had to screen the parts themselves, and their temp spec was very tight, but
it worked.  Another customer was dropping PIC's down a borehole where they
ran for a few minutes at some ungodly temperature like 300C.  Again, they
had to screen the parts themselves, but they got a tough job done.

> {Original Message removed}

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