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'[PIC]: 16F84A - 4MHz or 20MHz?'
2000\11\03@035530 by Bala Chandar

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I have a 16F84A pic waiting to be programmed. It is a standard 18 pin
plastic package. Can someone tell me the maximum frequency at which it can
be run?

The Product Line Card (for Qtr 2 2000) I received from Microchip shows the
maximum frequency for 16F84A as 20MHz. But the marking on the chip is
"PIC16F84A-04/P". Does "04" in the marking mean that its maximum frequency
is only 4MHz?

Thanks.

Regards,
Bala Chandar

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2000\11\03@035949 by Martin Hill

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The -04 means that the PIC is rated to 4MHz, it doesn't mean that it
won't run faster, just that it is only verified upto 4MHz, depending on
demand you might find that many parts are sold as 4MHz, but are
capable of running to 20.

Martin

{Quote hidden}

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2000\11\03@040400 by Andrew Warren

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Bala Chandar <spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU> wrote:

> the marking on the chip is "PIC16F84A-04/P". Does "04" in the
> marking mean that its maximum frequency is only 4MHz?

   Yes.

   -Andy


=== Andrew Warren - .....fastfwdKILLspamspam@spam@ix.netcom.com
=== Fast Forward Engineering - San Diego, California
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2000\11\03@123123 by hgraf

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> I have a 16F84A pic waiting to be programmed. It is a standard 18 pin
> plastic package. Can someone tell me the maximum frequency at which it can
> be run?
>
> The Product Line Card (for Qtr 2 2000) I received from Microchip shows the
> maximum frequency for 16F84A as 20MHz. But the marking on the chip is
> "PIC16F84A-04/P". Does "04" in the marking mean that its maximum frequency
> is only 4MHz?

    Yes, the 04 means it is a 4MHz max chip. Most PICs come in more than
one version, this allows small savings if you don't need full speed. TTYL

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2000\11\03@163552 by Jinx

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>>The Product Line Card (for Qtr 2 2000) I received from Microchip shows
>>the maximum frequency for 16F84A as 20MHz. But the marking on the
>>chip is "PIC16F84A-04/P". Does "04" in the marking mean that its max
>>imum frequency is only 4MHz?

IIRC this was how it was explained to me some time ago. Unless something
has changed, all PICs of the model are made from the same die, and each
individual part is tested for speed. The -04 parts are guaranteed to run at
4MHz, but may actually run much faster, perhaps even up to 20MHz. Or
if there's a surplus of 20MHz parts on the market, -20 parts may be marked
as -04 parts for purely economic/supply/inventory reasons. So unless you
know why a part is marked as -04, you can't say for sure what its maximum
operating speed will be. You could get lucky and have a -20 marked as a
-04. Somebody claimed last year on the list to have overclocked a -10 to
> 50MHz with no apparent problems

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2000\11\03@165646 by David VanHorn

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At 10:40 AM 11/4/00 +1300, Jinx wrote:
>>>The Product Line Card (for Qtr 2 2000) I received from Microchip shows
>>>the maximum frequency for 16F84A as 20MHz. But the marking on the
>>>chip is "PIC16F84A-04/P". Does "04" in the marking mean that its max
>>>imum frequency is only 4MHz?
>
>IIRC this was how it was explained to me some time ago. Unless something
>has changed, all PICs of the model are made from the same die, and each
>individual part is tested for speed. The -04 parts are guaranteed to run at
>4MHz, but may actually run much faster, perhaps even up to 20MHz. Or
>if there's a surplus of 20MHz parts on the market, -20 parts may be marked
>as -04 parts for purely economic/supply/inventory reasons. So unless you
>know why a part is marked as -04, you can't say for sure what its maximum
>operating speed will be. You could get lucky and have a -20 marked as a
>-04. Somebody claimed last year on the list to have overclocked a -10 to
>> 50MHz with no apparent problems


This sort of reasoning will get you in lots of trouble.

What you know from a -04 marking is that the device is guaranteed to
perform to spec up to that frequency. Beyond that, you're on your own.

The -04s may in fact be made on the same wafers as the -20s.
However, different parts of the wafer may perform better or worse than the
others.
This is why they test.

It's true that a given chip may run a given program at a given temperature
and VCC, at some higher clock speed.  However, you have no guarantee that
adding or removing a single instruction won't cause mysterious flakey
problems.

Debugging time is too precious to waste it trying to save a dollar on a
faster rated chip.

The approach I take for prototyping and hobby use, is to buy the fastest
grade chips.
Then, if a given project dosen't need the speed, I'll buy the lower grades
for production.  I'd rather save the $ on the bulk of the chips I buy,
rather than on the few I need for prototypes.


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2000\11\03@170534 by Bob Ammerman

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This has been discussed to death, but it is worth noting:

A -20 part is 'guaranteed' to work at 20Mhz across voltage and temperature
and phase of the moon.

The -04 part might go at 20Mhz at room temp, but die at a higher / lower
temp, voltage, etc.

For hobby use - feel free to push it.

If you put one in my pacemaker (or microwave oven), please stick to the
spec!

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2000\11\03@203445 by David VanHorn

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>For hobby use - feel free to push it.

I don't get it.. Why would you give yourself another potential headache for
a couple dollars?  My approach is to buy the fastest for protos, then use
what I need in production. I don't need any "mystery problems".

>If you put one in my pacemaker (or microwave oven), please stick to the
>spec!

100% agreement :)



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2000\11\03@205547 by Bob Ammerman

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>
> I don't get it.. Why would you give yourself another potential headache
for
> a couple dollars?  My approach is to buy the fastest for protos, then use
> what I need in production. I don't need any "mystery problems".

I wouldn't, but lots of people would. Take a look at the PC overclocking
world if you want to see what I mean.

Even for hobby work I would strongly suggest using in-spec chips in
development. But if they then want to try to push it...

{Quote hidden}

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>
>
>

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2000\11\03@213347 by Jinx

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> A -20 part is 'guaranteed' to work at 20Mhz across voltage and
> temperature and phase of the moon.
>
> The -04 part might go at 20Mhz at room temp, but die at a higher /
> lower temp, voltage, etc.

I was careful to say "guaranteed", and I keep -04 -10 and -20 parts
around. For > one-offs I would always use spec parts, life's complicated
enough. Microchip aren't going to be sympathetic if you use O/S parts
and have problems

Did try some -10s once to see what they would go up to and IIRC didn't
find one that would go past 15MHz with a simple LED flash program.

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2000\11\05@233900 by Bala Chandar

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Thanks a lot to all those who responded to my query about the maximum speed
of PIC 16F84A-04/P.

About a year back, I first came to know about PIC microcontrollers after
seeing them used in X10 home automation devices. Being an electronics &
computer hobbyist, I got really interested in PICs and searched the Internet
and collected as much information as possible on the PICs. I also ordered
and received the CD and the Product Line Card from Microchip. I was keen to
buy a flash PIC and had to wait for three months to get the 16F84A in the
local market (Bombay, India).

Though according to some the "-04" PIC can be overclocked to even up to
20MHz, I will use it at the rated speed of only 4MHz. That will ensure that
my PIC stays alive and I continue to learn about it through my projects and
experiments!

Thanks & regards,
Bala Chandar

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2000\11\06@002948 by staff

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Bala Chandar wrote:
{Quote hidden}

I thought it was interesting when someone mentioned that the
20MHz parts may be re-badged as 4MHz etc to suit sales
demand. Is there a way to test this? What about just overclocking
it until it starts to fail and that might tell?? I have never
overclocked a PIC so I wouldn't even know what to look for
when it starts to fail... Thermal shutdown? Program crashes?
Keeps resetting?? The "inquiring mind" part of me would like to
know EXACTLY what my PICs are, not just what was written on them
for marketing purposes. :o)
-Roman

PS. I suppose it would be nice to know at what speed a 4MHz chip
starts to fail, and what speed a 20MHz chip starts to fail. Anyone
know the speeds?

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2000\11\06@055928 by Andy Howard

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From: "Roman Black" <.....fastvidKILLspamspam.....EZY.NET.AU>
To: <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Monday, November 06, 2000 5:30 AM
Subject: Re: [PIC]: 16F84A - 4MHz or 20MHz?



> I thought it was interesting when someone mentioned that the
> 20MHz parts may be re-badged as 4MHz etc to suit sales
> demand. Is there a way to test this? What about just overclocking
> it until it starts to fail and that might tell?? I have never
> overclocked a PIC so I wouldn't even know what to look for
> when it starts to fail... Thermal shutdown? Program crashes?
> Keeps resetting??

It'd probably need to be more rigourous than just ramping up the clock to
discover if it was a rebranded 20MHz part.  You could, e.g., have code to
exercise all parts of the PIC then run it at a variety of voltages and
temperatures with real-world type loads and/or inputs.

As others have said, for the small difference in price it's worth getting
the right part for the job and having peace of mind.


.

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2000\11\06@071337 by Bob Ammerman

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This just won't die!

How much do you think Mchip has invested it the equipment they use to test
PICs for speed before marking them.

I expect it would be _far_ cheaper to buy -20 parts than to replicate
Mchip's testing to make sure your -04 will work reliably at -20.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2000\11\06@072801 by Martin Hill

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I'm with you Bob, I sell parts running at 16MHz, wouldn't dream of
using anything other than 20MHz parts for the job.  It's just not worth
it.  If you have a few 4MHz parts lying around, sure it's OK to play
around with them and see what they can do, but not for something
which is going into production.

So how fast can a PIC run then?  22? 24? 26MHz?

Martin
{Quote hidden}

> {Original Message removed}

2000\11\06@080722 by staff

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Bob Ammerman wrote:
>
> This just won't die!
>
> How much do you think Mchip has invested it the equipment they use to test
> PICs for speed before marking them.
>
> I expect it would be _far_ cheaper to buy -20 parts than to replicate
> Mchip's testing to make sure your -04 will work reliably at -20.
>
> Bob Ammerman


I appreciate the professional atittude, I too am a professional
and use certified 20MHz chips running at 16MHz in our product.

But don't you want to KNOW?? I have bought a number of -10P and
-4P PICs, and I really would like to know if I got what I paid for
or if I got something else.

I don't want to run a 4MHz chip at 20MHz. But if I bought 4MHz chips
that are actually 20MHz chips I would like to KNOW. :o)
-Roman

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2000\11\06@114910 by Dwayne Reid

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At 12:08 AM 11/7/00 +1100, Roman Black wrote:

>But don't you want to KNOW?? I have bought a number of -10P and
>-4P PICs, and I really would like to know if I got what I paid for
>or if I got something else.
>
>I don't want to run a 4MHz chip at 20MHz. But if I bought 4MHz chips
>that are actually 20MHz chips I would like to KNOW. :o)
>-Roman

Actually, I think that you are looking at it backwards.  I'm pretty sure
that testing goes something like this:

Test to 20 MHz - those that r l , mark as such.
Test to 4 MHz - those that pass, mark as such.
Toss the rest.

When they have more than enough 20 MHz parts sitting in inventory, skip
step #1 above.

So you have 2 possible choices: your 4 MHz parts either failed 20 MHz
testing in some fashion *or* your 4 MHz parts were never tested above 4 MHz.

My understanding from speaking with the FAEs is that they sell far more 4
MHz parts than 20 MHz parts and that the majority of 4 MHz parts might well
work at speeds faster than what is stamped on the package.  But you would
never find me shipping product that contains an over-clocked PIC.

Maybe I'm weird, but I tend to purchase the fastest parts available for
development work and prototypes and re-use those parts over and over
again.  Its money well spent.  If I need to go fast, I can and do.  But
once I get the project to the final stages, I try to re-work things so that
a 4 MHz part works.  I can think of only 2 projects that I've been involved
with that needed to ship with fast parts - everything else uses 4 MHz parts.

dwayne





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2000\11\06@122852 by Kevin Blain

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How about

0. Test at 4 MHz
1. Mark as 4 MHz part or bin it.
2. Sell it.

Unless, if short of 20MHz part, then test at 20MHz. If pass, mark
accordingly

{Original Message removed}

2000\11\06@125337 by David VanHorn

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At 05:17 PM 11/6/00 +0000, you wrote:
>How about
>
>0. Test at 4 MHz
>1. Mark as 4 MHz part or bin it.
>2. Sell it.
>
>Unless, if short of 20MHz part, then test at 20MHz. If pass, mark
>accordingly


Of course you have access to the die, and the manufacturer's test routines,
and check across the full specified range of VCC and temperature, right?



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2000\11\06@162006 by Don Hyde

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Last year I went to the uChip Master's, and this question came up.  The
answer then was:

The difference is testing -- or more accurately, passing the tests.

They set out to make all the chips work at 20 MHz, full industrial range.
After the first few batches, pretty much all of them do make it.  But, if
there are any changes in the process, frequently, for a while, more chips
fall in the 4MHz commercial bin, and less make it to the 20MHz industrial
bin.

When you pay for faster parts and industrial temp range, it's not so much
the testing (they likely all got the same testing).  You are paying for
Microchip's guarantee that they meet the spec you bought to.

Pretty much all parts work that way.  That's why the fine print says "meets
or exceeds..."

> {Original Message removed}

2000\11\07@042023 by staff

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Don Hyde wrote:
>
> Last year I went to the uChip Master's, and this question came up.  The
> answer then was:
>
> The difference is testing -- or more accurately, passing the tests.
>
> They set out to make all the chips work at 20 MHz, full industrial range.
> After the first few batches, pretty much all of them do make it.  But, if
> there are any changes in the process, frequently, for a while, more chips
> fall in the 4MHz commercial bin, and less make it to the 20MHz industrial
> bin.
>
> When you pay for faster parts and industrial temp range, it's not so much
> the testing (they likely all got the same testing).  You are paying for
> Microchip's guarantee that they meet the spec you bought to.
>
> Pretty much all parts work that way.  That's why the fine print says "meets
> or exceeds..."


So really, the 4MHz parts and 10MHz parts are the ones that
the manufacturer has found to be faulty, or MORE faulty.
Do the failures that cause them to be sold as reduced speed
parts have any other effects? ie, whatever die problems
caused it to fail, could cause other unreliability??

I'm glad we are only buying 20MHz parts now. I wouldn't
want to put reject parts in our products.
-Roman

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2000\11\12@142143 by Nabil Benhadj

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yes the marking -04P means that it is for 4MHz at the most.


/nabil
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