NVRAM chip code burned and loaded in circuit or out of circuit?

Discussion in 'General Electronics Chat' started by SamEricson, Apr 28, 2015.

  1. SamEricson

    Thread Starter Member

    Apr 25, 2015
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    How do you get the code from a NVRAM chip? because if I remove the NVRAM chip from the circuit board it will lose it's code

    You use a universal programmer to burn code into NVRAM chips, but they will loose the code once you remove it from the universal programmer so how do you burn the code into NVRAM chips while it's soldered into the circuit board with a new battery installed
     
  2. dl324

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    Mar 30, 2015
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    Technically an NVRAM chip would have it's own battery; either self contained or attached to the chip so they remove as a unit. Dallas Semiconductor had both varieties. Chips with integral batteries and a unit that attached to an SRAM. In this case, you can remove the chip and use an appropriate programmer to read and/or write the contents. My hobbyist programmers include support for some NVRAM chips.

    Some devices have enough backup (usually a capacitor) that give you tens of seconds to change the battery. I've used many devices that would retain memory long enough to change batteries. Of course, you can't let the batteries run down completely...
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    NVRAM means non-volatile RAM which means it is not volatile which means it retains its contents when you remove primary power.
     
  4. SamEricson

    Thread Starter Member

    Apr 25, 2015
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    So only certain universal programmers will read and write NVRAM chips? not all universal programmers will read and write NVRAM chips

    Why does it need a NVRAM need a battery?

    I thought when the battery was low or bad the NVRAM lost it's saved settings and memory
     
  5. dl324

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    Mar 30, 2015
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    Technically non volatile means power isn't required to retain memory. What you seem to be talking about is NVRAM implemented as battery backed SRAM. Those devices do need a battery. They can call them NVRAM because the battery is integral to the package.
     
  6. Hypatia's Protege

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    Mar 1, 2015
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    Shades of the Icom IC-745 and its ilk -- in their case, however, the battery was um... less than integral -- So... with the battery so went the firmware!... :eek::rolleyes:

    With jaded regards
    HP:)
     
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
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    nvram is usually a matrix of fuses, you blow the fuses to set the data using a higher than normal voltage to write. so they must be probrammed out of circuit. then thy are put in the circuit and have their data permanantly inside, thats why they are non volatile. some are a little different, more like eproms, and can be programed in circuit, but not erased or reprogrammed.
     
  8. Hypatia's Protege

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    I belive the above described technology is termed PROM (Programmable Read Only Memory) or OTP (One Time Programmable) whereas NVRAM properly refers to either FLASH or EEPROM?

    Best regards
    HP
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    nvram is non volatile, meaning not re programable. eproms can be erased with ultraviolet, and flash can be rewritten also. they are nonvolatile in a way, by not loosing their memory when the power is turned off, but also proms do not loose their memory either.
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Non-volatile means that it doesn´t lose its contents without applied power. Ability to be reprogrammed is a completely different issue.
    For examle a harddisk or FRAM is a type of NVRAM. EEPROM is a type of NV ROM.
     
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  11. dl324

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    There are "degrees" of non-volatile. EPROM, EEPROM, and FLASH are considered non-volatile, but they are all subject to charge loss due to imperfections in the dielectric of the storage cells. When programmed correctly, they're spec'ed to retain data for 10-20 years. Charge loss can also be caused by X-rays, etc; any method that imparts sufficient energy to the trapped electrons so they can jump the barrier.
     
  12. Hypatia's Protege

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    Indeed! FWIW 27-series OTPs are, in fact, nothing more than windowless 27-series UV-eproms --- I've had very good experience erasing said devices via moderate irradiation by bremsstrahlung/'characteristic' spectra peaking at Ca. 80kev -- Contrary to some technical literature, I've not observed evidence of component degradation owed to this method over the course of several years and many erasure/program 'cycles' :)

    Best regards
    HP
     
    Last edited: Jan 5, 2016
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  13. dl324

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    When Intel was studying their invention of the EPROM, they determined that erasing with X-Rays damaged the oxide and that an annealing step was required to repair it. They decided that using a quartz window and UV to erase would be more reliable, not to mention more convenient, for end Users.
     
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  14. Hypatia's Protege

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    Interesting! I was unaware the manufacturer contemplated said technique -- thus it seems I've 'reinvented the wheel' as it were...:cool:

    In case anyone is interested, my procedure consists of placement of several devices within the main-beam path at a (mean) distance 20 CM of the collimator (i.e. ~ 40 CM from the beam port) --- thence operation of the tube (large filament at full temp, anode potential a flat 80KV) for a 'dose' of 700 Gy at the lowest (i.e. most distant) tray (aproximately 3 minutes with my apparatus). At the stated exposure I have never experienced reprogramability diffaculties, subsequent data retention failure or other reliability issues - despite many cycles --- Though, when I had occasion to sell erased OTPs as 'blanks', I made it a point to advise purchasers that the devices had been erased via 'nonstandard methods' and, further, that anticipated reliability should not be equated to that of new devices (I'll have a gold star, please! ;))

    PLEASE NOTE: By 700 Gy, above, I mean that exposure at the end of which an (ion-chamber type) dosimeter registers a 'dose' of 700 Gy --- Which is not to imply that the chips absorbed 700J per KG of Mass!!! --- Dosimeters are 'calibrated ' for organic matter (Spec. human tissue) and are nowhere near accurate for other substances!!! --- Still, it is convenient to use such instruments inasmuch as all (quality) dosimeters exhibit standardized response -- Note also that, while, in principle, any dosimeter technology (responsive to the spectra in question) will suffice, ion chamber based units tend to be the only (commonly available) instruments exhibiting sufficient range. --- Although 700Gy represents a trivial amount of energy, it is, nonetheless, productive of immense biologic effect! Hence the apparent 'hyper sensitivity' of dosimetry instrumentation...

    In closing --- It goes without saying that significant hazards attend operation of equipment productive of intense ionizing radiation and high power/high EMF electrical conditions - please don't ask me for design or construction advice... :(

    Best regards
    HP:)
     
    Last edited: Apr 29, 2015
  15. dl324

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    It was probably Dov Frohman who first did or proposed X-ray as a way to erase. The actual discovery of EPROMs was serendipity. Someone forgot to place a contact and design rule checkers weren't very common, or sophisticated if they existed, back then. Knowing the group he was working in, they were probably trying to make an SRAM or DRAM array.
     
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  16. Hypatia's Protege

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    So... 'twas "The Imp of The Floating Gate" acting for good!:D

    Well hey! Many thanks for the background info! To paraphrase Sydney Smith: "What I don't know would make a great book" --- A volume, I might add, well worth the read!:)

    Best regards
    HP
     
    Last edited: Apr 30, 2015
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