EPROM over erasing

[Slater]

Is it possible to damage an EPROM by exposing it to UV light for too
long? What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?

 

[Ian Field]

"Slater" <nontelo@dico.no> wrote in message
news:502e85e0.12851921@nntp.aioe.org...

Is it possible to damage an EPROM by exposing it to UV light for too
long? What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?

The old ceramic packaged one's must be getting hard to find these days - can
flash ROMs be put in their place?

 

[Wolfgang Allinger]

On 17 Aug 12 at group /sci/electronics/repair in article sogt28h4s3c6a8ojon4jkf04lmq1sjt5fp@4ax.com
<jeffl@cruzio.com> (Jeff Liebermann) wrote:

It might be helpful if you disclosed the manufacturer and model
number.

Oh no, that`s an ultra secret: burn before reading!

SCNR



Saludos (an alle Vernünftigen, Rest sh. sig)
Wolfgang

--
Wolfgang Allinger, anerkannter Trollallergiker reply Adresse gesetzt!
Ich diskutiere zukünftig weniger mit Idioten, denn sie ziehen mich auf
ihr Niveau herunter und schlagen mich dort mit ihrer Erfahrung!
(lt. alter usenet Weisheit)

 

[Jeff Liebermann]

On Fri, 17 Aug 2012 18:05:29 GMT, nontelo@dico.no (Slater) wrote:

Is it possible to damage an EPROM by exposing it to UV light for too
long?

No, and certainly not with a typical UV EPROM eraser with a typically
4watt UV lamp. Typical of most erasers is about 15mW/cm2 at 254nm for
15 minutes. Crank up the output much more and you'll smell ozone but
still won't burn out the EPROM. If the EPROM was manufactured using a
UV exposure masking process, typical UV levels during manufacture are
12watts/cm2.

What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?

It's a bad EPROM. If the blank check on your unspecified EPROM burner
says it's not blank, it's not blank. The mostly likely culprit is
wrong settings on your unspecified model EPROM burner. It's also
possible for something in the circuit, or ESD to blow up the EPROM.
It's also possible that your unspecified EPROM burner has a weak UV
lamp and did not erase the entire EPROM. My favorite was having the
label peel off and stick to the lamp inside my Data-Erase cheapo
eraser. That cast a rather large shadow and caused numerous bad
erasures. I didn't find the label until I took it apart to replace
the lamp.

It might be helpful if you disclosed the manufacturer and model
number.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Lee Gleason]

"Slater" wrote in message news:502e85e0.12851921@nntp.aioe.org...

Is it possible to damage an EPROM by exposing it to UV light for too
long? What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?

I left some 25C64's In my manually controlled (that is, no timer) UV
eraser for a couple of weeks, when I forgot to turn it off. They all still
programmed and worked fine.

--
Lee K. Gleason N5ZMR
Control-G Consultants
lee.gleason@comcast.net

 

On Friday, August 17, 2012 11:05:29 AM UTC-7, Slater wrote:

Is it possible to damage an EPROM by exposing it to UV light
for too long? What if a portion of the EPROM stays unprogrammed
('FF') and the chip goes through some program-erase cycles?
The unprogrammed area should fail sooner or later, shouldn't it?

I used only sunlight (Phoenix, AZ, 32N latitute, sky probably 90% clear), and for EPROMS written with all 0s, over 90% of the bits would erase in a day, 100% in 2 days, so I'd erase for 3-5 days. One summer I left a couple of EPROMs outside for a couple of months straight, and they all worked when I wrote all 0s to them, and the programming didn't take longer than for my other EPROMs, according to the programming method described in a TI data book, where a short programming pulse was used while the normal 5V supply went to 6V and the byte was tested after each write.

 

[Jeff Liebermann]

On Fri, 17 Aug 2012 16:40:00 -0700 (PDT), larrymoencurly@my-deja.com
wrote:

I used only sunlight (Phoenix, AZ, 32N latitute, sky probably 90% clear),
and for EPROMS written with all 0s, over 90% of the bits would erase
in a day, 100% in 2 days, so I'd erase for 3-5 days.

In the late 1960's, I was working on a nifty new product that included
some of the first EPROMs. The prototype was done and the boss
declared that it was time to take a proper photograph for the product
release, manuals, promos, literature, etc. After the photographers
with their bright lights were done, I couldn't make it work. I
eventually determined that all the EPROMs had at least been partially
erased. My guess is about an hour under the very bright lights. I
didn't see the lights but suspect they could have been arc lamps as
incandescent lamps doesn't have enough UV content to erase EPROMs.
Installing a spare set of EPROMS got it working again. After that
experience, I made it a habit of putting labels over the EPROM window.



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Phil Hobbs]

Jeff Liebermann wrote:

On Fri, 17 Aug 2012 16:40:00 -0700 (PDT), larrymoencurly@my-deja.com
wrote:

I used only sunlight (Phoenix, AZ, 32N latitute, sky probably 90% clear),
and for EPROMS written with all 0s, over 90% of the bits would erase
in a day, 100% in 2 days, so I'd erase for 3-5 days.

In the late 1960's, I was working on a nifty new product that included
some of the first EPROMs. The prototype was done and the boss
declared that it was time to take a proper photograph for the product
release, manuals, promos, literature, etc. After the photographers
with their bright lights were done, I couldn't make it work. I
eventually determined that all the EPROMs had at least been partially
erased. My guess is about an hour under the very bright lights. I
didn't see the lights but suspect they could have been arc lamps as
incandescent lamps doesn't have enough UV content to erase EPROMs.
Installing a spare set of EPROMS got it working again. After that
experience, I made it a habit of putting labels over the EPROM window.

_Foil_ labels. Paper sometimes wasn't opaque enough.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

 

[mike]

On 8/17/2012 11:05 AM, Slater wrote:

Is it possible to damage an EPROM by exposing it to UV light for too
long?
yes

What if a portion of the EPROM stays unprogrammed ('FF') and the

chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?
yes

 

[Jeff Liebermann]

On Fri, 17 Aug 2012 21:45:44 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Jeff Liebermann wrote:

On Fri, 17 Aug 2012 16:40:00 -0700 (PDT), larrymoencurly@my-deja.com
wrote:

I used only sunlight (Phoenix, AZ, 32N latitute, sky probably 90% clear),
and for EPROMS written with all 0s, over 90% of the bits would erase
in a day, 100% in 2 days, so I'd erase for 3-5 days.

In the late 1960's, I was working on a nifty new product that included
some of the first EPROMs. The prototype was done and the boss
declared that it was time to take a proper photograph for the product
release, manuals, promos, literature, etc. After the photographers
with their bright lights were done, I couldn't make it work. I
eventually determined that all the EPROMs had at least been partially
erased. My guess is about an hour under the very bright lights. I
didn't see the lights but suspect they could have been arc lamps as
incandescent lamps doesn't have enough UV content to erase EPROMs.
Installing a spare set of EPROMS got it working again. After that
experience, I made it a habit of putting labels over the EPROM window.


_Foil_ labels. Paper sometimes wasn't opaque enough.

Agreed. I still have a lifetime supply of 5 1/4" floppy disk write
protect tabs. Most are black vinyl(?) or some opaque black plastic
over paper. They go on easily, and remove without leaving a mess.

Incidentally, I just remmembered that I once won an arguement whether
a stick arc welder will erase an EPROM. An Intel 2764 was used
because I had plenty of them. My guess is that it takes about 2
minutes of exposure to trash the EPROM and about 10 minutes to totally
erase it. Keeping an arc going for 10 minutes was impossible, but 15
seconds at a time was easy enough. I also managed to get slag on
every EPROM, but that was expected.

When I tried to use some of the test EPROMs later, I found that I had
zapped some cells. I don't know how I did that since I shoved the
leads into a crumpled block of aluminum foil.

Assuming 200A at about 10V across the arc, that's 2000 watts. My wild
guess is about 1/10th of that is UV. Assuming a spherical radiation
pattern, a distance of about 10 cm, and an old EPROM chip size of 0.25
cm^2 chip area, the UV power density is very roughly:
Surface area of sphere =
4 Pi r^2 = 4 * 3.14 * 10cm^2 = 1256 cm^2
Power density
= 2000 watts / 1256 cm^2 / 0.25 * 1/10 = 0.64 watts/cm^2
That's 130 times the UV that's delivered by the typical 15mw EPROM
eraser. I would have expected it to erase the EPROM 130 times faster,
but that didn't happen.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[c4urs11]

On Sat, 18 Aug 2012 00:19:28 -0700, Jeff Liebermann wrote:

Incidentally, I just remmembered that I once won an arguement whether a
stick arc welder will erase an EPROM. An Intel 2764 was used because I
had plenty of them. My guess is that it takes about 2 minutes of
exposure to trash the EPROM and about 10 minutes to totally erase it.
Keeping an arc going for 10 minutes was impossible, but 15 seconds at a
time was easy enough. I also managed to get slag on every EPROM, but
that was expected.

Somewhere in the 80s I salvaged a proprietary controller in a steel sheet
cutting machine using this. We were rushing a repair late at night in the
middle of nowhere in France. About three sticks managed to wipe 8 devices.
It needed some convincing the customer though, he believed I was joking.
The nicest part was the French cuisine afterwards ;-)

 

[Slater]

Jeff Liebermann <jeffl@cruzio.com> wrote:

What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?

It's a bad EPROM. If the blank check on your unspecified EPROM burner
says it's not blank, it's not blank.

I meant another thing: what will happen if a chip undergoes several
write/erase cycles where an area is intentionally left unprogrammed
every time? It's like erasing it over and over.
Probably nothing, I think. It must have happened quite often that some
byte (or bit, why not?) would always be unprogrammed at every cycle in
the prototyping process, so it shouln't be a problem.

 

[Jeff Liebermann]

On Sat, 18 Aug 2012 18:10:08 GMT, nontelo@dico.no (Slater) wrote:

Jeff Liebermann <jeffl@cruzio.com> wrote:

What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?

It's a bad EPROM. If the blank check on your unspecified EPROM burner
says it's not blank, it's not blank.

I meant another thing: what will happen if a chip undergoes several
write/erase cycles where an area is intentionally left unprogrammed
every time? It's like erasing it over and over.

Nothing will happen. Erasing sets all the bits to a "1". If the bits
are already set to "1", then erasing won't change or wreck the bit.

EPROMs do have a limited number of erase cycles. It really depends on
the age and technology of your unspecified EPROM. Usually it's about
1000 erase cycles before the silicon dioxide wrapped around the gate
falls apart.

Probably nothing, I think. It must have happened quite often that some
byte (or bit, why not?) would always be unprogrammed at every cycle in
the prototyping process, so it shouln't be a problem.

Well, there's an easy test. Erase your unspecified EPROM. Verify
that every byte is set to FF with the blank check on your unspecified
model EPROM eraser. Create a bin file where all the bytes are
programmed to "OO". Write the file to the EPROM and compare the bin
file with a read from the EPROM. If they're identical, then the
programmer was able to change every cell and there are no bits stuck
at "1". If there are any bytes NOT set to "00", you have at least one
stuck bit.



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Geoffrey S. Mendelson]

Jeff Liebermann wrote:

Well, there's an easy test. Erase your unspecified EPROM. Verify
that every byte is set to FF with the blank check on your unspecified
model EPROM eraser. Create a bin file where all the bytes are
programmed to "OO". Write the file to the EPROM and compare the bin
file with a read from the EPROM. If they're identical, then the
programmer was able to change every cell and there are no bits stuck
at "1". If there are any bytes NOT set to "00", you have at least one
stuck bit.

Joining this late, I want to mention that the 27C series EPROMS can still
be bought. You can buy them from China for about $2 each including postage
for erased and tested "pulls" and new ones can be had for around $45.

They even come in the small flat packages that are common these days.
(sorry, it's late at night, and I don't remember their name)

I specifically needed 27C256's and 27C512's, last summer, so I bought an
eraser for around $15, a USB programmer for under $50 (including the adaptor
for flat packaged chips) and a bunch of $2 chips.

The eraser was an odd combination of a 230 volt unit with a US 120 volt plug,
and a mechanincal timer with a separate on off switch. I replaced the plug
with one more appropriate for my needs and just leave the timer in the
always on position, using an electronic kitchen timer and the on/off switch.

Geoff.


--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379

 

[whit3rd]

On Friday, August 17, 2012 11:05:29 AM UTC-7, Slater wrote:

Is it possible to damage an EPROM by exposing it to UV light for too

long?

Yes, sometimes. The reason is, EPROM designs sometimes use
difference amplifiers with dummy cells that are factory-programmed
and covered with a light-tight lid. So, if enough light leaks around
the lid, the bias of the sense amplifiers changes (and the chip can
become incapable of proper readout).

It's a matter of bleaching out the bias current sources...

 

[Jeff Liebermann]

On Sat, 18 Aug 2012 22:04:03 +0000 (UTC), "Geoffrey S. Mendelson"
<gsm@mendelson.com> wrote:

Joining this late, I want to mention that the 27C series EPROMS can still
be bought. You can buy them from China for about $2 each including postage
for erased and tested "pulls" and new ones can be had for around $45.

Yep. I just stocked up on 27C512 EPROMS (for Kantronics TNC's) at
about $1.50/ea it took about 2 weeks to arrive. All 20 were good.
However, I had to peel the original labels and UV erase them.

They even come in the small flat packages that are common these days.
(sorry, it's late at night, and I don't remember their name)

Atmel or Winbond AT27C512
http://www.ebay.com/itm/330561223626

I specifically needed 27C256's and 27C512's, last summer, so I bought an
eraser for around $15, a USB programmer for under $50 (including the adaptor
for flat packaged chips) and a bunch of $2 chips.

I have a Willem version 5.0 programmer.
<http://www.ebay.com/itm/370640611286>
Highly recommended. There's also the 6.0 version, which allegedly has
more features and requires fewer adapters:
<http://www.ebay.com/itm/221106449319>

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Cydrome Leader]

Ian Field <gangprobing.alien@ntlworld.com> wrote:

"Slater" <nontelo@dico.no> wrote in message
news:502e85e0.12851921@nntp.aioe.org...
Is it possible to damage an EPROM by exposing it to UV light for too
long? What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?


The old ceramic packaged one's must be getting hard to find these days - can
flash ROMs be put in their place?

how long can those old ceramic+window things keep their memory? Some spec
sheets indicate some random number of decades, but is any of this true?

 

[Ian Field]

"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:k1c45e$jsi$3@reader1.panix.com...

Ian Field <gangprobing.alien@ntlworld.com> wrote:


"Slater" <nontelo@dico.no> wrote in message
news:502e85e0.12851921@nntp.aioe.org...
Is it possible to damage an EPROM by exposing it to UV light for too
long? What if a portion of the EPROM stays unprogrammed ('FF') and the
chip goes through some program-erase cycles? The unprogrammed area
should fail sooner or later, shouldn't it?


The old ceramic packaged one's must be getting hard to find these days -
can
flash ROMs be put in their place?

how long can those old ceramic+window things keep their memory? Some spec
sheets indicate some random number of decades, but is any of this true?

I have an old XT-turbo clone with UV EPROMs that still works.

 

[Sjouke Burry]

Cydrome Leader <presence@MUNGEpanix.com> wrote in
news:k1c45e$jsi$3@reader1.panix.com:

Ian Field <gangprobing.alien@ntlworld.com> wrote:


"Slater" <nontelo@dico.no> wrote in message
news:502e85e0.12851921@nntp.aioe.org...
Is it possible to damage an EPROM by exposing it to UV light for too
long? What if a portion of the EPROM stays unprogrammed ('FF') and
the chip goes through some program-erase cycles? The unprogrammed
area should fail sooner or later, shouldn't it?


The old ceramic packaged one's must be getting hard to find these
days - can flash ROMs be put in their place?

how long can those old ceramic+window things keep their memory? Some
spec sheets indicate some random number of decades, but is any of this
true?



Two BBC2 computers and an ARC310 with numerous chips loaded with

software have survived 20+ years, and still going strong.

 

[Jim Yanik]

Cydrome Leader <presence@MUNGEpanix.com> wrote in
news:k1c45e$jsi$3@reader1.panix.com:

Ian Field <gangprobing.alien@ntlworld.com> wrote:


"Slater" <nontelo@dico.no> wrote in message
news:502e85e0.12851921@nntp.aioe.org...
Is it possible to damage an EPROM by exposing it to UV light for too
long? What if a portion of the EPROM stays unprogrammed ('FF') and
the chip goes through some program-erase cycles? The unprogrammed
area should fail sooner or later, shouldn't it?


The old ceramic packaged one's must be getting hard to find these
days - can flash ROMs be put in their place?

how long can those old ceramic+window things keep their memory? Some
spec sheets indicate some random number of decades, but is any of this
true?

flash memory(NOT a "ROM" aka Read-Only Memory) is not going to have the
same pinouts,because one pin has to have the write enable command that a
PROM lacks.

--
Jim Yanik
jyanik
at
localnet
dot com