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Thread: Simple old DRAM (4146, 41256) memory tester

  1. #1
    Join Date
    Dec 2012
    Location
    Russia, Moscow
    Posts
    132

    Default Simple old DRAM (4146, 41256) memory tester

    Hello,

    I want to introduce my simple DRAM memory tester based on PIC16F73 microcontroller. Possible replacement: PIC16F870, PIC16F873 and PIC16F876.
    DRAM tester can test 4164 (565RU5 exUSSR) and 41256 (565RU7 exUSSR) DRAM IC. Tester has two working mode: "simple LEDs" and "advanced UART".

    • simple LEDs: DRAM tester when power on autodetect inserted IC type (4164/41256). The LEDs blink four times. Then begin infinite loop testing; GREEN led turn off when pattern writing to DRAM and turn on when pattern reading from DRAM and comparing to etalon. If at some point the error occurred, RED led is turn on an still lighting until tester power off.
    • advanced UART: For use this mode you need TTL compatible level UART cable, so MAX232 based is good choice, and COM port in your desktop. Advanced UART mode allows control refresh time, set manual IC type, set tests mode (patterns, running '1', running '0'), view errors and more. Still debuging, not avalible in current project stage.. UART display errors at current moment only. Serial settings is 9600bps-1N8.


    Todo:
    1) static (6116, 6132, 6164) memory tests. Need add some extra component to board, such as tri-state 8 bit register for multiplexing address/data line. Need more space in PIC program EPROM, so PIC16F870 is't good choice. Low priority, because the static memory tests even in the Willem programmer.

    2) Add exotic DRAM chips, such as very old MOS 40965DC or exUSSR 565RU3. This chips have tripple power lines: +5, -5 and +12V. It will lead to a complication of the circuit power supply. Low priority.
    Attached Images Attached Images
    Attached Files Attached Files

  2. #2

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    Great work!

    I agree with static RAMs left apart; but the triple powered ICs would be a great addition (4116 are really common); sadly, as you already pointed out, the power circuit would be a bit more complex

    And what about the 4bit IC RAMs (4464, 44256)?, are they hard to implement?

  3. #3

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    This is interesting! I have recently looking into the subject of testing ICs before I solder them into place. The issue came up while repairing an old HP9810 calculator. I put a NOS RIFA (!) 7432 chip in as a replacement for the failing National Semiconductor DM7432. The RIFA chip was even worser than the NS chip...

    So I figure that I need a TTL tester. Then I also recognized that I have a lot of old 2102, 2114, 2147, 2101, 2148, 4096, 4116, 1103 and various other chips that is in questionable status. I need a quite generic IC tester. I did some searching and the I found the TL866 EPROM programmer. The bad news with this is that the amount of TTL chips it supports is quite limited but the good news is that someone has started on reverse engineer it. There were also a simple firmware that could be used as a starting point for own experiments.

    It only has two power supply generators. But it would't be to difficult to add another one.

    So what sense does it make to test TTL chips? Isn't just as easy to buy them new, someone might ask? Well, sometimes standard TTL chips (especially 74H and Signetics N8xxx) are really hard to find. And these that you find might not be in best shape.

    My route forward on this subject is to get a TL866 (approx $50) and making my own firmware.

    Except for this interesting homebuilt solution by Tronix, what are others using for IC testing?

  4. #4

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    I have since i bought it new in the '80 an HiLo ALL-02.
    It can test some TTL logic chips and some memory chips.

    Frank

  5. #5

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    Hello, I'm planning to build this tester and I have a question: What methods are used for memory test (zero/one-fill, what patterns)?

    ->MattisLind
    For testing TTL (and some SRAM) chips, the only capabilities for tester are to supply logic states on some pins and to read from another. Timings are critical for DRAM, but for SRAM chips testing can be slower. I am using a tester published in Everyday Practical Electronics (October 2002) with my own software in Qt (because the original one was in Visual Basic, doesn't run in Linux and has problems in newer versions of Windows).
    This tester is a bit slow. It can't be seen while testing 74LS00, but when testing e.g. some bigger one-way counter (to flip all output lines), testing takes few minutes. To test 2114, I'm doing standard fill then bit-walking and few passes of verification with random data. For my tester it takes about a minute for a chip to have one full-chip write/read pass.

  6. #6

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    Greetings to all the vintage gurus et al.

    I would definitely be interested in a RAM tester. Who's taking orders?

    Thanks.

  7. #7

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    Quote Originally Posted by MattisLind View Post
    This is interesting! I have recently looking into the subject of testing ICs before I solder them into place....So I figure that I need a TTL tester. Then I also recognized that I have a lot of old 2102, 2114, 2147, 2101, 2148, 4096, 4116, 1103 and various other chips that is in questionable status. I need a quite generic IC tester.
    What about a DIL ZIF socket on a Raspberry Pi board (the B+ has 26 usable GPIO's).

  8. #8

    Default

    I haven't built this yet, but tried PIC software with with debugger - do I understand this tester properly?
    Is it writing address as data and reading it back?
    What if error bit is "stuck" at address bit?

  9. #9
    Join Date
    Dec 2012
    Location
    Russia, Moscow
    Posts
    132

    Default

    Hello,

    In attachment firmware source code. Compile with PIC CCS (trial)
    Attached Files Attached Files

  10. #10

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    I use a memory expansion board and CheckIt to weed out bad memory chips. It's easy and it can verify NINE chips at a time! Of course if you have a bad one in the mix you need to do some fishing. But when they're all good it's really fast.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

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