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Thread: Reading a flaky EPROM

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    Default Reading a flaky EPROM

    Has anyone come across this sort of situation before, and is there a solution?
    27C64 EPROM that I want to read the contents out of... freshly pulled out of working equipment, so I presume the EPROM is working too. Read it with my ancient but trusty DSE EPROM programmer and... different read result each time! Perhaps the DSE programmer is a bit long in the tooth, so I bought a new Willem based EPROM programmer. Same result - random read results each and every time. I've never seen an EPROM do that before.
    Any ideas?



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    Looks like a timing error. Check the baud rate and parity etc for the serial connection to the programmer.

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    Both programmers are parallel (LPT) based, but that does give me another idea - slow down the read. Perhaps the programmers are trying to read the contents too quickly. Its not possible - I don't think, anyway? - on the Willem to slow it down, but the DSE programmer, from memory there are things that can be done, though not sure if they only apply to writing or both read & write. Even if I use an old DOS 'slomo' type app to put the brakes on... might be worth a try?

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    Increase or decrease the delay time - set it until it reads correct. Most Programmers are dumb. What software are you using? MPLAB ?

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    For the Willem programmer - the software at mpu51.com, for Windows v0.97ja. The DSE had a DOS program written by Glenn Pure, v2.01.

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    The DSE one was an Electronics Australia project and designed by Jim Rowe. It will not work on latest computers, you will need an old 286 based system.
    This problem was discussed recently in Silicon Chip. I will see if I can find the question and answer.

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    I found the Silicon Chip item.
    The programmer was actually a Silicon Chip design.
    The problem lies with how the later versions of windows deals with the Centronics Parallel Port.
    They recommend using no later than XP, or getting a USB to Centronics adapter.

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    Yep, got the PC side of things covered... an old 486 laptop running Win95 with a real LPT port. Kept just for such purposes. Will have a play with the timing of the SC / DSE / EA Jim Rowe unit and see if I can get any sense out of it, and try a SloMo program with Wilem too. I'll report success, if any, later on.

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    These days, I just do this -->

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    Silly question. Is this Eprom the only one playing up? Others work.

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    Quote Originally Posted by Reschs View Post
    Silly question. Is this Eprom the only one playing up? Others work.
    Sure is. I had programmed some others back in the late 1990s, and they still read beautifully. Could be a dud EPROM, but as mentioned, it was freshly removed from working equipment.

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    Was it soldered in or in a socket ?

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    Quote Originally Posted by mitaux8030 View Post
    Sure is. I had programmed some others back in the late 1990s, and they still read beautifully. Could be a dud EPROM, but as mentioned, it was freshly removed from working equipment.
    Another silly question -- if it was working, why the need to remove/read the ROM?

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