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Ian Field

"mike" wrote in message
...
On 11/24/2012 5:20 PM, Leif Neland wrote:
har bragt dette til verden:
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),

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.

I'm a motorcyclist - I'd drive the tank along the line of parked cars.