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?

 

[Wolfgang Allinger]

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

 

[Lee Gleason]

"Slater" wrote in message news:[email protected]...

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.

 

[mike]

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

 

[c4urs11]

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]

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.

 

[Geoffrey S. Mendelson]

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.

 

[Cydrome Leader]

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?

 

[Sjouke Burry]

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.

 

[Leif Neland]

[email protected] har bragt dette til verden:

I used only sunlight (Phoenix, AZ, 32N latitute, sky probably 90% clear),

It never worked for me in Denmark, 56N

 

[mike]

[email protected] har bragt dette til verden:

It never worked for me in Denmark, 56N

It's an old thread, but I have a story and some time on my hands.

The erase is not the only problem. Charge can leak in or out
electrically too.
I had a TEK 308 logic analyzer that wouldn't run. I fixed it
by reading the EPROM in my reader, erasing it and putting the
same bits back in. The data was marginal and wouldn't run
at speed, but the programmer was slow enough that it worked.
I replaced the chip anyway.

The Compaq Aero laptops had a recurrent "motherboard failure".
I discovered that you could pull the EEPROM, read it
and reprogram it with the same data. That fixed it for
a random length of time. In that case, I think the cause
was that the program line was left floating. Some combination
of turnon/off transients let random "puffs" of charge into
whatever address happened to be on the pins and the thresholds
shifted over time until it failed to boot. I fixed several of them
by reprogramming. Replacing the chip didn't help.

I like the roadway analogy.
Spread gravel on a road. By the end of rush hour, there won't
be any gravel in the path of the tires. When a tire hits a bit of gravel,
it causes it to move in some random direction. If that direction
takes it out of the tire path, it quits moving. Statistically,
all the gravel eventually gets displaced out of the tire path.
The gravel got erased.
But the tires also damage the road. Bits of gravel get embedded
in the roadway and can't move out. Eventually, the roadway turns
to gravel and can't support the traffic. Getting just the right
amount of energy is critical for maximum life. That's why they
don't want you to drive a tank down a residential street.

 

[Leif Neland]

Michael A. Terrell kom med denne ide:

You are replying to a three month old message.

I know.

I still have 1500 out of 9000 messages to read, but I'm catching up

Leif

 

[Leif Neland]

Michael A. Terrell forklarede den 25-11-2012:

9000? I see a total of 237,016 messages for this group.

I only wanted to go back one year, when I discovered this group.

 

[josephkk]

Its abundantly clear from your arrogant attitude what you're like.

With the training and experience listed you still call him arrogant? I
don't think so. More like intolerant of a 'wanna be' blowing smoke.

?-)