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Forcefully erasing OTP chips... — Parallax Forums

Forcefully erasing OTP chips...

VaatiVaati Posts: 712
edited 2010-03-19 20:06 in General Discussion
Is it possible to forcefully erase an old OTP MCU/EPROM? I have an intel 87C42 that I am dying to program, but it's already been loaded with something and it isn't a UV windowed version...

Maybe if you apply 12 volts on pins 1-20 and connect pins 21-40 to ground... lol.gif

But seriously, is it possible? Has anyone tried?

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Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-03-17 22:16
    No, you can't erase it; you can only convert 1 bits to 0 bits. So if 00 is a NOP, and the chip is only partially programmed, you can program zeroes up to the unprogrammed part (which will be FFs), and begin programming from there.

    -Phil
  • VaatiVaati Posts: 712
    edited 2010-03-17 22:34
    So, how does EPROM work? How is the memory retained, and not re-writable?

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    Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!

    (no longer new) SD Card Adapter·Now available!· Add extra memory to your next Propeller project with ease!
  • kwinnkwinn Posts: 8,697
    edited 2010-03-17 22:49
    The charge is stored on a "floating gate". It is surrounded by insulation, but close enough to a transistor gate to affect the conductivity of that transistor when the gate is charged. Think of it as one plate of a capacitor.

    The only way to remove the charge once it is on the gate is to expose it to ionizing radiation (UV) which will bleed off the charge. I suppose X-rays or gamma rays would also work but I have never been curious enough to try that.

    The above statement is not quite accurate. The charge will bleed off very slowly over many years. The original 1702 eproms were notorious for erasing themselves after 10 or more years. The higher the operating temperature the sooner they became blank or partially blank. Some of that may have been due to not being programmed properly in the first place.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-03-17 23:45
    BTW, the EPROM in OTP chips is exactly the same as that in the erasable ones. The only difference is the package. Erasable chips are housed in much more expensive ceramic packages with quartz windows; OTP chips, in opaque plastic.

    -Phil
  • icepuckicepuck Posts: 466
    edited 2010-03-19 03:07
    Old Intel MCUs do have a way to re-use a OTP part by grounding a pin or tying it high that would bypass the internal rom and look for an external rom/eeprom.
    You will need the datasheet for your specific part in order to bypass the rom.
    -dan

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  • LeonLeon Posts: 7,620
    edited 2010-03-19 13:58
    I seem to remember people erasing them with X-rays, many years ago. I'd forget that old Intel chip and use one of the current 8051 variants, some of them can do 100 MIPS:

    www.silabs.com/products/mcu/pages/default.aspx#

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    Leon Heller
    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 3/19/2010 2:03:22 PM GMT
  • VaatiVaati Posts: 712
    edited 2010-03-19 20:06
    Ok--I have looked at that page many times, trying to get samples of those chips. smile.gif

    I did get a gameboy advance multiboot cable (http://www.ziegler.desaign.de/GBA/gba.htm#Multiboot) that has an Atmel 8051 clone in it, and I'm probably going to take that out and use it for something else.

    Also, is there a way to read the program from a 6052 or more specifically, a 6052 variant? smile.gif

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!

    (no longer new) SD Card Adapter·Now available!· Add extra memory to your next Propeller project with ease!
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