Can I reburn an OTP processor???

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Can I reburn a chip like the PIC12C508 OTP part?

Assume you have a jump table in high memory.
On powerup, the processor scans the table and jumps to the last
non-FF address.
Next time, you put the new code above the existing code in the
address space and add a jump vector to the table.
Or maybe overwirte earlier entries with 00 and
jump to ghe first nonzero address.

So, is there anything in the chip that would prevent doing this?
Would I have to rewrite the burner code to allow burning a non-blank part?
Maybe this code already exists?
thanks, mike
--
Return address is VALID.
500MHz Tek DSOscilloscope TDS540 $2200
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Re: Can I reburn an OTP processor???
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You can only reprogram 1 bits to 0.



Re: Can I reburn an OTP processor???
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And I'm too lazy to go look it up, but isn't 0x00 a NOP?  I remember
reading a trick to reprogram the OTP chips by leaving a gap at the
beginning (of 0xFF) and starting with a goto your code.  Then each time
you reprogram you turn the old goto into a nop and put a new one after
it.  I could be backwards and nop is 0xFF, but then you just put the
first goto at the end of the gap and work backwards instead.

I'm also too lazy to go price them but I bet a 12F629 is cheaper than
a 12C509 now.

--
Ben Jackson
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Re: Can I reburn an OTP processor???
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Yup., 0 is NOP on the PIC12.

Flash is sooo much better for development. Leave OTP parts for when you're
ready for mass production (and don't intend to upgrade).


Re: Can I reburn an OTP processor???
On 27 Nov 2004 12:35:12 GMT, the renowned snipped-for-privacy@aol.com (Gary Kato)

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There are even 12F508 parts available now (90 cents in 25's).


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
snipped-for-privacy@interlog.com             Info for manufacturers: http://www.trexon.com
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Re: Can I reburn an OTP processor???
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Hi,

No problem to do this, every decent programmer will jut ask if you
want to proceed and burn non-blank parts.
By the way Microchip OTP and Flash uC prices are almost the same so
this would be applicable if you have a lot of these old OTP chips.
12C508 have only 512 words of program memory, so I doubt is it worth
the troubles to re-compile your code at different memory offsets etc,
istead to buy one Flash part and re-program it thousands of times.

Best regards
Tsvetan
---
PCB prototypes for $26 at http://run.to/pcb
(http://www.olimex.com/pcb )
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Re: Can I reburn an OTP processor???


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Most people do the first N units with an EEPROM parts and then
go to OTP when they are sure that it works.  Do you have a special
application that makes you expect changes?  Or do you have a
problem with your process that results in poor requirements and
inadequate testing?

On that chip, NOP is all zeros, check the data sheet, but
I believe that it starts out all 0s and you can write only 1s.
[ http://ww1.microchip.com/downloads/en/DeviceDoc/40139e.pdf ]

It comes out of reset by executing whatever is a address zero
with page zero selected, so you can easily put in a bunch of
NOPs followed by a jump to your code, and later put in another
jump that gets executed first.

Your burner may choke on programming a non-blank part.
Check with the manufacturer.

Also, you can erase OTP parts by using X-Rays instead of UV.
Make friends with a dentist.

--
Guy Macon <http://www.guymacon.com


Re: Can I reburn an OTP processor???

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No you can't. The chip will be damaged by the energy needed to erase in any
realistic time.

Re: Can I reburn an OTP processor???


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I have heard this claim before, but have never seen any
references or citations supporting the theory.  

Would one of you IEEE members be so kind as to look at this
paper and see if it sheds light on this issue?
http://ieeexplore.ieee.org/xpl/abs_free.jsp?arNumber14%5016


Re: Can I reburn an OTP processor???
"Guy Macon" ...
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About 10 years ago I've programmed OTP micro's for a prototype and shipped
them from the Netherlands to Sweden. Customer complained - they failed to do
anything.
Programmed a few more, tested them: OK.  Sent them off. Same complaint.
Customer returns chips - they were empty and fully reprogrammable.
We sent another programmed and tested lot, now wrapped in Alu foil and with
a big sticker "DO NOT XRAY - SENSITIVE DEVICES". All devices worked on
arrival...

BTW: The dentist's Xray machine tube wears out relatively fast. I'm not sure
what the real cost of erasing would be...

Regards,
Arie de Muynck



Re: Can I reburn an OTP processor???

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That appears to be evidence that x-rays can erase OTP parts - something
that we already know to be true.  It sheds no light upon the claim that
x-rays *damage* OTP parts.  I am still looking for evidence to support
that particular claim.

Also, there have been many laptops with EPROMs in them going through
many airport x-ray machines for many years - some of them many times -
and the laptops still boot.  I would suspect that your programmer
was doing a marginal job.

--
Guy Macon <http://www.guymacon.com


Re: Can I reburn an OTP processor???




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Many years ago I had a big pile of OTP 27C512. That was a leftover from
    the upgrades of the EPSON printers. The unused memory in those parts
could be programmed just fine.

I tried to reuse those 27C512 by erasing them with the X rays. No luck
at all. The parts were partially damaged before getting completely
erased. I spent several days trying to find the optimal voltage, current
and exposure settings.

Indeed, the conventional 2764 with UV window was erased with X rays with
no problems at all.

Perhaps the silicon in the OTP parts is different from the ordinary
parts. It is not intended for multiple reprogramming.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

Re: Can I reburn an OTP processor???
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I think that OTP parts are tested while they are still on the die. They can
then be UV erased before being encapsulated.

Peter



Re: Can I reburn an OTP processor???
On Saturday, in article

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The difference between OTP and UV eraseable is just the package the die
is the SAME! Without the quartz window UV will not penetrate the ceramic or
plastic casing. A plain casing is cheaper to produce than one with a
quartz window.

One product many years ago was always giving problems on site, which was
tracked doen to the boards that failed had a quartz window. As the
customer had Beta radiation sources about that even penetrated the PC case
these cards would scramble themselves and generally had to be unplugged
and left for two days before being reused. We swapped out the eraseable
parts for OTP and the customer had no further problems.

--
Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
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Re: Can I reburn an OTP processor???



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That is a guesswork. How do you know?
It seems logical to use a lower quality silicon for the parts not
intended for reprogramming, isn't it?
My practical experience shows that it is not a good idea to erase OTPs
with X-ray machine.


Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

Re: Can I reburn an OTP processor???
On Sunday, in article
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Over the years, various discussions with distributors and manufacturers, and
in some cases past datasheets.

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You can test for speed of access, how are you going to test on wafer
how many times it is likely to programme, in a QUICK way. Many manufacturers
even on Flash parts have been conservative on how many times their devices
can be reprogrammed to cope with worst case situations. Many have changed
their specs from 100 times to 1000s of times from experience and more
extensive testing over long periods of time.

In reality it is easier to test the wafer that on reprogramming one or more
times, the cells respond and get to correct levels on wafer/die test points
for ALL types, then choose how to package as they do for all other devices.

It is more logical to manufacture and test for one die configuration and
spec, and it is more cost effective. Even RAM parts that notoriously had
many speed variants in the past to overcome yield problems and low margins
are being produced with less speed variants, to cope with the other
logistics problems of storing and handling speed variants, which adds to the
costs.

Plastic/ceramic OTP packaging is cheaper as more parts are packaged that
way. Windowed products are special cases and hence a different packaging
process(es).

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That maybe so which is different to the point I answered. Ever considered
how X-Ray transparent ceramic/plastic is compared to quartz, let alone any
heat dissipation or other characteristics that may be different.

Anyway why bother X-Ray work for the MAJORITY of people is very costly
and expensive, let alone hazardous.

--
Paul Carpenter          | snipped-for-privacy@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/ PC Services
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Re: Can I reburn an OTP processor???


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We had an incident years back where a series of OTP processors failed
in the field.  The manufacturer denied that this was possible.  We provided
samples for them to test.  Ultimately, they confirmed our claims and replaced
the processors.  One of the things that came out of this was a couple of OTP
parts that were converted to UV Erasable parts.  They used fuming Nitric acid
dripped onto the part to dissolve the PLCC encapsulation over the die.  This
formed a crater around the die, but left everything else intact. These parts
could
then be erased by UV.  We added a quartz window and Indium bond to one
and used it as a  UV erasable part for verification.  Still have it around here.

Blakely LaCroix


Re: Can I reburn an OTP processor???
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Or perhaps the 27C512 cells are much smaller than the 2764 ones and more
prone to damage due to exposure.

Regards.

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