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how easy is it to accidentally erase an eprom?

gophert

Well-Known Member
Most Helpful Member
#21
I don't think it's the age of the EEPROM that matters as much as how often it's been written or how long it's held the same data. I'd assume that an EEPROM that's 100 years old would work just as good as one that was brand new as long as the data it was holding was fresher and it's write endurance was not exceeded? No one ever talks about the age of the EEPROM itself...only it's data retention life and write endurance.
Nobody talks about it but has anyone ever tested two cycles of 30-year retention? I think it hasn't been on anyone's radar screen until recently. In summary, I'll assume your answer to my question is, "Folklore rules at this point."
 

MaxHeadRoom78

Well-Known Member
#22
Long story short. I was working on an industrial control cabinet yesterday outdoors. Basically a 4x4x8ft tall control cab and then a small PC type enclosure inside that. The PC box door came open so I blew out the dust in it. The sun was not really out much and I know no direct light hit the chips but I didn't even realize until today the friggin UV erase windows are NOT covered? Who does that? In a high end industrial device? A little sticker maybe?
Anyway, they have some rather important data on them so hoping we are OK?
The bottom line is don't let them expose themselves, make sure they have the proper covering at all times when you open the door!!:eek:
Max.
 

unclejed613

Well-Known Member
Most Helpful Member
#23
ut to be more serious, I understand his point - it makes sense to make backup's of a memory that has a finite life, who might only need a backup once in your life, but having one could be hugely valuable.
there were some banking machines that had a PC connected to them, either directly or over a network. some of the PC software checked for the proper firmware version on the machine before any further communication took place.
 

unclejed613

Well-Known Member
Most Helpful Member
#24
I don't think it's the age of the EEPROM that matters as much as how often it's been written or how long it's held the same data. I
we're now talking about a different beast. an EEPROM doesn't need UV exposure to erase it, but uses an erase voltage. there are a few basic types of devices commonly referred to as EPROMs (including two types that can't be erased):

PROM Programmable Read Only Memory. this device cannot be erased and is programmed only once. basically a matrix of "fuses", and once burned (as a matter of fact this device is the source of the terminology of "burning" a device) cannot be reprogrammed.

Masked PROM this device is programmed using an optical mask during the fab process. i think this process is only used in the manufacture of microprocessors and SOC devices.

EPROM Erasable PROM this is the device with an erase window. this is the type of device we've been discussing in this thread (mostly).

EEPROM Electrically Erasable PROM this device uses an erase voltage (often a higher voltage than what is normally used in the device during operation) to reset all the bits. some types require the higher voltage to be applied during programming as well.

Flash ROM this device is basically what a thumb drive is. it can be written, erased or changed at will using the normal operating voltage. also used as NVRAM (NonVolatile Random Access Memory).

this isn't an exhaustive list. there are many different sub-types and different techniques used, and they all have different data retention and re-usability characteristics (for instance there is a type of Flash that erases if the device is unsoldered).


with the EPROMs that are optically erasable, there is another reason to use a sticker over the window. silicon junctions are photosensitive, and an EPROM can develop "soft" errors if the chip is exposed to light during operation. i've actually had this happen where a machine would operate normally with the cabinet doors closed, but the machine would lock up if the doors were open. one of the EPROMs in the machine had lost it's sticker, and when exposed to light during operation, had a tendency to flip random bits. putting a new sticker on the EPROM solved the problem.
 

JimB

Super Moderator
Most Helpful Member
#25
i've actually had this happen where a machine would operate normally with the cabinet doors closed, but the machine would lock up if the doors were open. one of the EPROMs in the machine had lost it's sticker, and when exposed to light during operation, had a tendency to flip random bits. putting a new sticker on the EPROM solved the problem.
Wow, that is seriously weird!
That is one of those "faults" which could drive you insane.

JimB
 

unclejed613

Well-Known Member
Most Helpful Member
#26
That is one of those "faults" which could drive you insane.
it only showed up because the field tech was blowing dust out of it while the operator was using the machine. the bank and the field tech thought the tech had broken something.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
#27
Takes you back to the old germanium transistor days - where if you scratched the paint on an OC71 it became photosensitive - in fact you could make your own OCP71 (photo transistor) by removing the black paint from an OC71.
 

Pommie

Well-Known Member
Most Helpful Member
#28
Takes you back to the old germanium transistor days - where if you scratched the paint on an OC71 it became photosensitive - in fact you could make your own OCP71 (photo transistor) by removing the black paint from an OC71.
I remember doing that too. Was it the OC71 that had a red, orange or green dot dependant on the gain or was that an earlier device?

Mike.
 

MaxHeadRoom78

Well-Known Member
#30
Long ago a puzzled friend brought over his old transistor radio, he said that if he opens the back the volume goes way up.
Checked it and it had the familiar OC71's!!
Max.
 

dknguyen

Well-Known Member
Most Helpful Member
#31
Long ago a puzzled friend brought over his old transistor radio, he said that if he opens the back the volume goes way up.
Checked it and it had the familiar OC71's!!
Max.
It's a feature so when you play the radio to go to sleep, it slowly gets quieter as it gets darker outside.
 

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