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'CODE PROTECTION for Mr. PIC Average.'
1997\04\29@093927 by Jim Robertson

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Hi Folks,

I'm not interested in getting into a superfluous argument on code
protection, especially on the PICLIST where the subject has been handled
quite wildly in the past.

However, I am a little bit worried where the last thread "Protected Bit in
16C74/JW" ended up. I really don't want to see people misled and lose their
JW parts so here is something that hopefully will make me feel I've done my
duty to my PICLIST peers...



If we are being practical, devices with "unerasable code protection" really
should be treated as such. It is misinformation for anyone to state
otherwise. Please don't think you can code protect an "unerasable" and
somehow erase it later "with just a little extra effort." You will be in
for a rude shock!

Personally, I have never heard of a case of a unerasable device being fully
erased in anything like 2-3 hours. If it has ever happened it's very
untypical.

Regarding the previous discussion on the PICLIST centering around a 16C74.
I cannot honestly see how anything that was said suggested the 16C74 was an
"A" part. All the evidence I saw suggested it was not (no mention of an "A"
and the fact that it did erase in the expected time frame for a non "A"
16C74.)

Any conclusion that the eventual successful erasure of this part indicated
that unerasable code protect parts could be erased seems faulty to me.

For the sake of a more accurate picture I venture the following antidotes:

I heard of one experiment done with a fully protected part where SOME of
the multiple code protect bits were erased after several DAYS of UV but
other bits in the same device didn't move after a full week of UV.

Personally I have a code protected 14000 that has "lived" in my eraser for
months without showing the slightest sign of the one programmed CP bit
erasing. (Maybe it's because I don't believe in fairies, santa claus or
"erasable unerasables!") :~)

I do believe the above examples are usually what you can expect with
unerasable CP parts. Please do not let antidotes of occasional exceptions,
engineering samples, X ray exposure, faulty observation etc. etc. confuse
you. For "Mr. PIC Average" with the normal, usual tools unerasable means
unerasable and you will save time, money and frustration by adhereing to
this most humble wisdom.


BTW. There are a number of programmers available that will safe guard the
code protect bits with default lockouts, overrides and warning messages
etc. I do think such things are necessary for piece of mind at the very least.

That's it from me! I'm out of here...

Jim

1997\04\29@161455 by Mike Smith

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----------
> From: Jim Robertson <spam_OUTnewfoundTakeThisOuTspamIACCESS.COM.AU>
> To: .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
> Subject: CODE PROTECTION for Mr. PIC Average.
> Date: Wednesday, 30 April 1997 14:08
>

> Personally I have a code protected 14000 that has "lived" in my eraser
for
> months without showing the slightest sign of the one programmed CP bit
> erasing. (Maybe it's because I don't believe in fairies, santa claus or
> "erasable unerasables!") :~)
>

Months?  UV tube lifetimes are rated in *hours* , and not too many, either.
I wonder how many erasers out there have tubes that are significantly down
in UV output.  I should add that I haven't had *any* experience with these
magical "erasable unerasables!") :~) either! (but I did wonder about the
tube life)

Mike Smith
(mikesmith_OZspamKILLspamrelaymail.net)

1997\04\29@163938 by mbonner

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Mike Smith wrote:

 ----------
 > From: Jim Robertson <.....newfoundKILLspamspam.....IACCESS.COM.AU>
 > Personally I have a code protected 14000 that has "lived" in my
 eraser for months .....

 Months?  UV tube lifetimes are rated in *hours* , and not too many,
 either.
  I wonder how many erasers out there have tubes that are
 significantly down
 in UV output.  I should add that I haven't had *any* experience with
 these
 magical "erasable unerasables!") :~) either! (but I did wonder about
 the
 tube life)

 Mike Smith
 (EraseMEmikesmith_OZspam_OUTspamTakeThisOuTrelaymail.net)

I've been using a Spectroline eraser for over a decade (!) with the
_same_ tube and it erases _erasable_ PIC16C74As in 10 minutes.
-Matt

--
Matthew Bonner B.Eng.
Product Development Engineer
Sunada Technology Corp. Calgary, Alberta
mbonnerspamspam_OUTsunada.com

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