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'[PIC] : 16F877 vs 16F877A'
2005\11\16@234513 by alan smith

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Did some searching.....and havent found a real good description of the 877A updates.  From what I know, it has changes in the programming algorithims, and it fixes a problem with the PORTB read/modify/write but what else?

               
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2005\11\17@084102 by Mauricio Giovagnini

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The PIC16F877A has a comparator, and the 77 doesn't
     I also remember having read on the Microchip forum and some websites that the A have a better algorythm for 'code protection'.
   They also have an enhanced eeprom and flash, that will give you more writing cycles.
       alan smith <spam_OUTmicro_eng2TakeThisOuTspamyahoo.com> escribió:Did  some searching.....and havent found a real good description of the 877A  updates. From what I know, it has changes in the programming  algorithims, and it fixes a problem with the PORTB read/modify/write  but what else?

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2005\11\17@090506 by rosoftwarecontrol

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when programming A, it goes faster than non A also.

code protection, mean nothing to code breaker.
There are always more way to break than to protect it.





{Original Message removed}

2005\11\17@140616 by Maarten Hofman

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> code protection, mean nothing to code breaker.
> There are always more way to break than to protect it.

I take this to mean: "Code protection means nothing to the code
breaker. There are always more ways to break code than there are to
protect it."

As far as I understood there are indeed more ways to break the code
protection of a PICmicro than there are to protect it (basically you
just set the fuse). I list three that I can think of:

1) Analysis of the read result. The microcontroller mangles the result
significantly, using XOR of previous and future values, making it
impossible to one-to-one map the values to instructions. However, with
knowledge of typically used assembly instructions, or the high level
language used, it is probably possible to figure out part of the code
this way. Unfortunately, this will most like result in the more
obvious code and some instructions around it. It seems to be that this
is very time consuming, and most likely not the most efficient way to
get to the code.
2) Opening the packaging, and taking a magnified picture of the code
memory. This is probably faster, although it could result in the
destruction of the chip and still would require considerable counting.
3) Opening the packaging, and using a laser or other mechanism to
change the code protection fuse back to "unprotected". This seems to
be the easiest way to retrieve the code (apart from going beyond the
PICmicro and hacking into the system that generated the code to begin
with), though there is an increased risk of damage to the PICmicro.

Note that none of these three options are "nothing": they all take a
considerable amount of effort and work, and it might often be less
expensive to buy the product. The code protection fuse therefore has a
valid use, and improvements of the scheme (which make option 1 more
difficult) are useful as well.

Greetings,
Maarten Hofman.

2005\11\17@152313 by Mauricio Giovagnini

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I agree, and... its really too costy to do the point 2) or 3).
   The common case to do this I think isn't to buy or not the product, but to steal the code and do some businesses with it...
 
Maarten Hofman <.....cashimorKILLspamspam@spam@gmail.com> escribió:  > code protection, mean nothing to code breaker.
> There are always more way to break than to protect it.

I take this to mean: "Code protection means nothing to the code
breaker. There are always more ways to break code than there are to
protect it."

As far as I understood there are indeed more ways to break the code
protection of a PICmicro than there are to protect it (basically you
just set the fuse). I list three that I can think of:

1) Analysis of the read result. The microcontroller mangles the result
significantly, using XOR of previous and future values, making it
impossible to one-to-one map the values to instructions. However, with
knowledge of typically used assembly instructions, or the high level
language used, it is probably possible to figure out part of the code
this way. Unfortunately, this will most like result in the more
obvious code and some instructions around it. It seems to be that this
is very time consuming, and most likely not the most efficient way to
get to the code.
2) Opening the packaging, and taking a magnified picture of the code
memory. This is probably faster, although it could result in the
destruction of the chip and still would require considerable counting.
3) Opening the packaging, and using a laser or other mechanism to
change the code protection fuse back to "unprotected". This seems to
be the easiest way to retrieve the code (apart from going beyond the
PICmicro and hacking into the system that generated the code to begin
with), though there is an increased risk of damage to the PICmicro.

Note that none of these three options are "nothing": they all take a
considerable amount of effort and work, and it might often be less
expensive to buy the product. The code protection fuse therefore has a
valid use, and improvements of the scheme (which make option 1 more
difficult) are useful as well.

Greetings,
Maarten Hofman.

2005\11\17@161541 by Mark Rages

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On 11/17/05, Mauricio Giovagnini <maugiovagninispamKILLspamyahoo.com.ar> wrote:
> I agree, and... its really too costy to do the point 2) or 3).
>

#3 will cost at least $50 + UV eraser:

http://www.bunniestudios.com/wordpress/?page_id=40

Regards,
Mark
markrages@gmail
--
You think that it is a secret, but it never has been one.
 - fortune cookie

2005\11\17@173806 by Wouter van Ooijen

face picon face
> I agree, and... its really too costy to do the point 2) or 3).

I recently saw a link to page of someone who claimed to have selectively
erased the security bits of some FLASH PIC (IIRC an 18F). He opened up
the chip, identified the fuses bits with a microscope, put black masking
tape over the rest, and exposed the die long enough to UV to erase the
fuses bit. He used nothing more fancy that a microscope, steady hands,
and some UV source. I guess most PIClister could reproduce his work if
they wanted.

> #3 will cost at least $50 + UV eraser:
> http://www.bunniestudios.com/wordpress/?page_id=40

I knew someone would come up with the link :)

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\17@185321 by Bob Axtell

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Wouter van Ooijen wrote:

{Quote hidden}

These kinds of things remind me of all the links for a car that runs 100
miles on
a gallon of water... lots of pictures and neat arrows, but no  substance.

Look, trust me on this one... There is no RELIABLE way to crack a PIC's
code.
I know, I have spent a LOT of time trying...

--Bob

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2005\11\17@213956 by Mark Rages

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On 11/17/05, Bob Axtell <EraseMEengineerspam_OUTspamTakeThisOuTcotse.net> wrote:
> >>http://www.bunniestudios.com/wordpress/?page_id=40
>
> These kinds of things remind me of all the links for a car that runs 100
> miles on
> a gallon of water... lots of pictures and neat arrows, but no  substance.

Really?  Bunnie has a pretty solid reputation.  He is the author of
that book on X-Box hacking, for example, and together with the EFF
reverse engineered the color laser watermark.

> Look, trust me on this one... There is no RELIABLE way to crack a PIC's
> code.
> I know, I have spent a LOT of time trying...

Did you try the method depicted in the link?

Regards,
Mark
markrages@gmail
--
You think that it is a secret, but it never has been one.
 - fortune cookie

2005\11\17@221710 by Bob Axtell

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Mark Rages wrote:

{Quote hidden}

No, I didn't try that. I'm getting OUT of the hardware end of PICs. But
I did a study for a
client a few years back, and chased a few methods, and found no reliable
crack for PIC16C..

However, in my estimation, whatever code protection is there now is
probably weaker than
before... The newer NanoWatt parts have inherent problems, the worst
being the EEPROM
losing data bits, requiring keeping some data in several places; so it
stands to reason
that somebody could crowbar something and get it to work now and then.

Doing something once or twice is interesting but not reliable. I would
not invest in anybody
offering to crack PICs as a business. Note: if you crack a US Military
PIC product, those
swell guys from a 3-letter agency will be all over you like flies on
manure.

--Bob


{Quote hidden}

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2005\11\18@021117 by Wouter van Ooijen

face picon face
> Look, trust me on this one... There is no RELIABLE way to
> crack a PIC's code.
> I know, I have spent a LOT of time trying...

You are caught by a frequently occuring logic error. The fact (I have no
reason to assume it is not a fact) that you have tried hard but not
found a reliable cracking method gives some support to the theory that
no such method exist, but it simply can't provide proof.

And note that a reliable method is not needed. In nearly all cases where
one might want to carck a PIC one can get a number of copies and try a
method with a certain success rate.

And last: did you try the method outlined on that page and found it
wrong? If so in what way?

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\18@041540 by Alan B. Pearce

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>Note: if you crack a US Military PIC product, those
>swell guys from a 3-letter agency will be all over
>you like flies on manure.

Do Microchip do any MIL spec PICs? If not then the above scenario is very
unlikely.

2005\11\18@062253 by Mauricio Giovagnini

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Doing something once or twice is interesting but not reliable. I would not invest in anybody
offering to crack PICs as a business. Note: if you crack a US Military PIC product, those
swell guys from a 3-letter agency will be all over you like flies on manure.
I think that there are a lot of inescrupulous people around the world.
 The fact is that if you have a massive product whoose intelectual  property belongs to you, and someone hacks your pic and steals the code  and then he can reproduce the code a thousand times... you will be out  of business before even realizing what they did to you.
   This is the biggest fear a developer will face.
   And im thinking that if your product is not massive but the revenues  are high, then another people will try to steal your code !!
   I have seen this kind of attempts on electronic controlled industrial  printers!  I mean the machines for doing books and so.  May  be the people can automate 100 machines a year but the revenues are  huge! so... they attempt to steal the code of someone that puts his  effort and knowledge on it.
   This is what the chip developers should put effort on.   If  the code protection can be so kind of easily violated... then we must  point to another brand of micrcontrollers.
             

               
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2005\11\18@081010 by Rodrigo Real

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Mauricio Giovagnini <KILLspammaugiovagniniKILLspamspamyahoo.com.ar> writes:

Hi guys

I had a problem with these new version, with the 'A'.

I work with a motor controller, and when I swithced from 16F877 to 16F877A
I had electric interference which made the PIC resets and get crazy
sometimes.
I could solve these isolating a bit more the logic part and the power
side of my circuit, but it was a little hard. And in fact I am not
sure if I won't have problems with that in a near future.

Rodrigo

{Quote hidden}

> -

2005\11\18@084048 by Mauricio Giovagnini

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Can you reproduce the exact problem? when it happens?
     I read on the Microchip forum, many months ago that the 77 series are more inmune to noise.     If its electrical, then check putting some capacitors here and there.
   An inductor in series should work also.
   If your problem is related to magnetic interference, not electrical, then consider using a faraday shielding.
     
Rodrigo Real <spamBeGonerodrigospamBeGonespamfreedom.ind.br> escribió:  Mauricio Giovagnini  writes:

Hi guys

I had a problem with these new version, with the 'A'.

I work with a motor controller, and when I swithced from 16F877 to 16F877A
I had electric interference which made the PIC resets and get crazy
sometimes.
I could solve these isolating a bit more the logic part and the power
side of my circuit, but it was a little hard. And in fact I am not
sure if I won't have problems with that in a near future.

Rodrigo

{Quote hidden}

> -

2005\11\18@101742 by Spehro Pefhany

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At 08:17 PM 11/17/2005 -0700, you wrote:


{Quote hidden}

The companies that do this commercially want a few units with the same code
to work on.

Microchip has been trying to improve the code protection, but there are
places with
sophisticated equipment and it doesn't take that long or cost that much to
use it.
You shouldn't bet too much that a PIC (or any other 'normal'
microcontroller) won't
be hacked. Put easter eggs and other signature things in the code, at a
minimum, and
you may be able to halt sales of a pirated product in places with strong IP
laws.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
TakeThisOuTspeffEraseMEspamspam_OUTinterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
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2005\11\18@103032 by Bob Axtell

face picon face
Spehro,

I lost parts of the piclist threads over the last few days because of HD
cleanup going
on. Was there a  method of code protection that worked in other ways,
such as clipping
PB7?

Might breach the moisture protection though, if  clipped very close.

Actually, I think this is an important topic. Other ideas?

--Bob

Spehro Pefhany wrote:

{Quote hidden}

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2005\11\18@125036 by Spehro Pefhany

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At 08:30 AM 11/18/2005 -0700, you wrote:
>Spehro,
>
>I lost parts of the piclist threads over the last few days because of HD
>cleanup going
>on. Was there a  method of code protection that worked in other ways, such
>as clipping
>PB7?

There was some talk of burning out the protection diodes, IIRC, but I
suspect you could
drive them to the right logical level with enough current, and burning them
out might
cause reliability issues. Clipping the lead wouldn't stop anyone for more
than minutes-
a pointed pogo pin in a quickie MDF fixture would make reliable contact,
and it's
even possible to solder a fine magnet wire on, even if it was cut flush
(I've actually
done this on a TQFP PIC in an emergency when the tiny pin was broken off
flush!). If not,
simply remove the epoxy and connect to the leadframe.

>Might breach the moisture protection though, if  clipped very close.
>
>Actually, I think this is an important topic. Other ideas?
>
>--Bob

I suppose it is, but I think that if your 'foe' has access to a few
thousand or tens of
thousands of dollars worth of equipment, there is very little that you can
do with "normal"
microcontrollers to make them immune to cracking. You can lock your house,
but a
person or group who really wants to get in, and has the equipment and
know-how, will
be able to get in rather trivially.

There are some micros with design flaws (IMHO) that can be 'cracked' by
fiddling the
pins in certain ways outside of datasheet specifications, and those would
be best
avoided if you're concerned about security. OTOH, I don't think there's a
mainstream
micro which can't be cracked in one way or another for the cost of a few
weeks of
work, or less, in North America. Even the sophisticated protection on DVDs
and Adobe's encryption were broken fairly readily, by individuals working
alone IIRC.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
EraseMEspeffspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\11\20@145449 by Steph Smith

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standard practice with old TTL 'jelly bean' logic I.C.'s was one bypass cap.
(0.1uF) in parallel with the power supply smoothing cap. (100uF),AND a 100nF
between each supply as close as possible to EACH I.C. to filter out mains
hum and short spikes on the supply rails.This 'rule of thumb' still holds
true.
{Original Message removed}

2005\11\21@153618 by Rodrigo Real

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"Steph Smith" <RemoveMEzapsmithEraseMEspamEraseMEblueyonder.co.uk> writes:

Hi

> standard practice with old TTL 'jelly bean' logic I.C.'s was one bypass cap.
> (0.1uF) in parallel with the power supply smoothing cap. (100uF),AND a 100nF
> between each supply as close as possible to EACH I.C. to filter out mains
> hum and short spikes on the supply rails.This 'rule of thumb' still holds
> true.

I was already doing this with the 16F877, but with this new one, I had
to isolate the grounds (high current side from logical side) with an
inductor.



> {Original Message removed}

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