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Thread: Problem reading/writing EPROM

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    Problem reading/writing EPROM

    Hi

    I am trying to burn an EPROM (ST M27C160) but it's consistently failing. I noticed that when I read a blank M27C160 EPROM on my reader, it always reads like this:

    FFBF FFBF FFBF...

    all filled with this pattern. Of course, when I write the EPROM, it writes fine, but it fails the verification. Funny thing is: the bits that fail the verification are not always the same that show wrong when the EPROM is empty. Sometimes they are, but sometimes they check fine.Things I have tried:

    - Using a different version of the software (TOPWin 6 and TOPWin7, my programmer is a TOP3000)
    - Using a different PC to connect the programmer. Same problem.
    - Using different EPROM models: I tried reading empty D27C1001D, M27C4002, 27C010A, and D27C1000A, all read perfectly (all FFFF)
    - Using different USB cable to connect the programmer. Problem persists.

    I am at a loss here guys, any suggestions are welcome.

    Thanks!!

  2. #2
    Choi's Barber
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    You're using the ac adapter to power it right?

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    Quote Originally Posted by kuze View Post
    You're using the ac adapter to power it right?
    Yes, however I have not tested that it's working. Any idea how many volts should it throw? I see no marks on either the programmer or the adapter itself.

    Thanks!!

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    The programmer only needs the extra power for writes, reads should be fine with just the 5V on the USB.
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    Quote Originally Posted by DNSDies View Post
    Most EPROMs write at either 9v or 12v
    I tested the adapter and is throwing 5V. It seems to be the right voltage, so that should be OK, however no clue how the adapter may get 12V from a 5V adapter.

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    Quote Originally Posted by aha2940 View Post
    Yes, however I have not tested that it's working. Any idea how many volts should it throw? I see no marks on either the programmer or the adapter itself.

    Thanks!!
    Not sure, I know some chips require 12v. You could try topwin8 and updating your firmware to the latest version. I haven't had any issues with 27c160 chips on mine.

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    Quote Originally Posted by kuze View Post
    Not sure, I know some chips require 12v. You could try topwin8 and updating your firmware to the latest version. I haven't had any issues with 27c160 chips on mine.
    Do these thingies have firmware? where do I get it? how do I update it? I tried to use TOPWin8, but the laptop I use with the programmer does not have ability to run it, therefore I'm stuck with 7 or 6.

    Thanks!!

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    Quote Originally Posted by aha2940 View Post
    Do these thingies have firmware? where do I get it? how do I update it? I tried to use TOPWin8, but the laptop I use with the programmer does not have ability to run it, therefore I'm stuck with 7 or 6.

    Thanks!!
    Maybe it doesn't update the fw, but there's an 'update' tool in topwin that will get you the latest version, the English manual covers using it. You can get the manual from their site. http://topwin6.com/Soft-1.html

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    JammaNationX
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    The programmers use DC-DC voltage converters. I use mine solely on the USB power and I write 160 and 322s no problem.

    When you say it's reading blank as FFBF, is the programmer verifying it as black or are you just reading the 160? Either the 160 is bad or you might need a better eraser, use one that actually has a bulb and not LEDs.

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    Hi dudes,

    Your problem can be the eprom itself. Sometimes the eprom is dead. I assume that you are referred to the same eprom. Have you tried it with another 160?

    @James the problem is when try to verify. I suppose that the blank check is passed first.

    Un saludo
    Last edited by fremen; 03-29-2015 at 04:55 AM.
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    Hi guys, I'll try to clear the questions here:

    - I have tried 5 different EPROMs. 2 I have cleared them myself, the other 3 came clear from the buyer. All 5 exhibit the same FFBF pattern.
    - The blank test fails. It fails in the second byte, because it reads BF instead of the expected FF. Same byte fails during the verification (after writing).
    - The EPROMs write without throwing any error.
    - My EPROM eraser is a small chinese plastic box, which has a mechanical chronometer and a fluorescent tube inside (looks like a fluorescent tube, I know it is not).

    Thanks for your help so far guys, very appreciated.

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    Blanking in topwin shouldn't be necessary as long as the EPROM has already been fully erased. I'd try erasing one for a half hour, then reposition it at a 90 degree angle and give it another half hour. Then read the chip in topwin to confirm it is fully erased before trying to write again.

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    Hi,

    Thank you for the clarifications. A couple questions, how long for erase a 160?? I use 40-45 minutes.
    Do all of them have the same serial numbers?? Some of them have an X and some programmers have problems with them

    Un saludo
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    Too much UV exposure to an eprom can damage it. Not sure how long a 27c160 should be exposed to blank fully, but an hour in total sounds a bit too much?

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    Quote Originally Posted by DNSDies View Post
    I'd write 00s to the EPROM before erasing it though, just to be safe.
    With my two programmers (one a Wellon, the other a Top some number I can't remember) you can't write to it if it doesn't pass the blank check. And even when it is being written in this case, it's coming back as FFBF all the way through.

    How would writing 00s protect it?
    Last edited by pulstar; 03-29-2015 at 11:42 AM.

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    Quote Originally Posted by DNSDies View Post
    It has to do with how UV light charges the cells in an EPROM to set them to 1, and how UV light can "overcharge" a cell when overexposed, making it unclearable (stuck at 1).
    By writing 0s, you're actually clearing the charges from it, so you run less of a risk of overcharging an already charged cell.

    Also, are these CMOS EPROMs?
    Those are a little finicky with supply and programming voltages (needs 6v and 12.5v).
    Ah right, cool info, didn't know that...but if the eprom isn't writing properly it makes it a little difficult to write 00's (and also, once an eprom is written you can't change the info until you UV erase it anyway)...27c160's should be CMOS (I think) .
    Last edited by pulstar; 03-29-2015 at 01:25 PM.

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    Hi

    Some more clarifications:

    - The "blank" on my programmer, only tests if the EPROM is blank, it does not blank it. It has to be blanked with an UV eraser.
    - The EPROMs are all CMOS (they are 27C160, C is for CMOS AFAIK).
    - I leave EPROMS about 15-20 mins on the eraser to get them blank. I read 5 minutes should be enough, and that too much time can damage the EPROM.
    - My writer will write even if you don't do the blank test. I guess it will blindly write what it's on the buffer, even if it writes right or not.
    - All the 160 EPROMS I've tested are ST M27C160-100F1. I have not tried other brands of 160s.
    - I have tried reading the EPROMs as ST and also as generic 160 EPROMs. Same results with both.

    Thanks!!

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    Try filling the buffer with AAAA and see if that burns and verifies.
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    Quote Originally Posted by bustedstr8 View Post
    Try filling the buffer with AAAA and see if that burns and verifies.
    Hi

    Just did the test, it writes and verifies fine.

    Thanks!!

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    Hi,

    Your problem is the erase time, try 45 minutes.

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    Quote Originally Posted by aha2940 View Post
    Hi

    Just did the test, it writes and verifies fine.

    Thanks!!
    I hate to quote myself, but I also tested writing to the same EPROM a buffer filled with 55 (without erasing it first). It wrote fine, and the EPROM now reads completely filled with 00 (that was expected, right?).

    Quote Originally Posted by fremen View Post
    Hi,

    Your problem is the erase time, try 45 minutes.

    Un saludo
    I'll try to erase the previous EPROM for 45 minutes and try again, however I've read online that such a long erase time can damage the EPROM...

    Thanks!!

    Edit: on a second thought...if the problem was the erase time, wouldn't the incorrectly erased bits be random? I find it strange that all the erased EPROMs get the same FFBF pattern, and that also the EPROMs I just bought, that I have not erased (and they say are new, but who knows...) show the same pattern. I'm starting to think something went wrong with my programmer...
    Last edited by aha2940; 03-29-2015 at 06:04 PM.

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    Quote Originally Posted by aha2940 View Post
    I hate to quote myself, but I also tested writing to the same EPROM a buffer filled with 55 (without erasing it first). It wrote fine, and the EPROM now reads completely filled with 00 (that was expected, right?).

    Yes



    I'll try to erase the previous EPROM for 45 minutes and try again, however I've read online that such a long erase time can damage the EPROM...

    Thanks!!

    Edit: on a second thought...if the problem was the erase time, wouldn't the incorrectly erased bits be random? I find it strange that all the erased EPROMs get the same FFBF pattern, and that also the EPROMs I just bought, that I have not erased (and they say are new, but who knows...) show the same pattern. I'm starting to think something went wrong with my programmer...
    That's what I'm thinking. I had you write AAAA because it should bypass the bad bit.

    Try writing 5555 on a blank eprom if it's a bad bit I think it will read 5515
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    Quote Originally Posted by bustedstr8 View Post
    That's what I'm thinking. I had you write AAAA because it should bypass the bad bit.

    Try writing 5555 on a blank eprom if it's a bad bit I think it will read 5515
    You were absolutely right. After writing a buffer of only 55 to an EPROM, I got the EPROM filled with 5515. Now the problem is I don't know if the programmer is not writing the files right, or is simply reading them wrong...any way to know?

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    It's definitely not reading that bit correctly, you wouldn't fail to verify every blank you had.

    Only way I can think of to verify that you are still writing the proper data is to use another programmer or find someone to read a 5555 filled chip.

    If you can't find anyone close I have no problem doing it.
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    Quote Originally Posted by bustedstr8 View Post
    It's definitely not reading that bit correctly, you wouldn't fail to verify every blank you had.

    Only way I can think of to verify that you are still writing the proper data is to use another programmer or find someone to read a 5555 filled chip.

    If you can't find anyone close I have no problem doing it.
    Thanks for your help, bustedstr8. I'll consider your offer and maybe send you a couple chips to test, however that's not an option for every EPROM I write

    From what I've read, this M27C160 chip works with having a bit more than 1 million of 16-bit sections, which are addressable individually. So, you enter a number, from 0 to 2^20-1, in binary form, on the A lines (pins 1-10 and 33-42), being 0 a voltage of 0 (or very near it) and 1 a voltage of about 5 (or close to it) and you get the bits that section (sector?) contains, on the D (Q) pins, which seem to be pins 14 to 30 on this EPROM model. Therefore, it seems my programmer is reading wrong always the 6th bit (starting from 0) on all the 16-bit sections it reads (it always read 0, no matter what). Am I getting this right? if so, maybe this thing is easily fixable...what do you guys think?

    Thanks!!
    Last edited by aha2940; 03-29-2015 at 08:50 PM.

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