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EEPROM speech recorder/player

Discussion in 'Electronic Basics' started by Tim Porter, Jun 1, 2004.

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  1. Tim Porter

    Tim Porter Guest

    Hi all,
    I've designed a circuit which will record speech from a microphone and
    store it onto ROM. The circuit includes the ability to play, pause,
    rewind, alter the sample rate, and reverse the output.
    The circuit does NOT use a micro controller, and I dont want it to.
    It uses a binary up/dn counter for generating the address lines, and
    obviously a ADC and DAC for encoding/decoding, as well as some simple
    logic gates and a couple of latches.
    My design currently stores the speech data on an EEPROM at 16khz
    sample rate, and the databus is 8 bits wide.

    I have two questions:

    1) Is it actually possible to program a standrd 28xxxx serires EEPROM
    at this speed? In fact, whats the maximum speed these thing can be
    written too?
    I know they can be read very fast because ive already built a "play
    only" version which requires the PROM to be pre-burnt, and i can crank
    the sample rate up very high without a problem.

    2) Parallel EEPROMs seem very expensive, and I have an old 8MB SIMM
    lying around, but have no prior experience interfacing with them. I
    found a pinout and it seems simple enough, 11 address lines and 8 data
    Does it have a similar archetecture to an EEPROM? If so, I would
    definatly consider using it instead.

    I realise if I opt for the SIMM, the data will be lost at power down,
    but this isnt a major issue.
    Remember though, I dont want to use any uControllers.

    Thanks to anyone who can offer their advise.

  2. -----------------------
    Sure, you can use the SIMM, but there are problems with using DRAM,
    which is what a SIMM is. You need to research DRAM refreshing, and
    here is a URL of a similar device that uses DRAM for a reverb/echo
    using the same kind of approach as you like:

    You might want to use parallel cache SRAM instead, it's simpler.
    I've built a bunch of stuff in the manner you suggest. Another
    means of storage would be to incorporate an EPROM burner into
    your design, and use the counters to burn from SRAM to EPROM.

    Check out my site's EPROM refs for how-to:

  3. Rich Grise

    Rich Grise Guest

    I have no idea - what does that data sheet say?
    Yes, you can read with the speed of a memory bus - what's that, hundreds
    of MHz these days? Well, I'd still look it up. I don't know how fast
    EEPROMs are.
    I'm not that familiar with SIMMS, but I'm ass-u-me-ing that they're
    dynamic RAM, and personally I wouldn't want to try to interface a
    dynamic RAM.
    Then I _really_ wouldn't recommend dynamic RAM. Have you looked into
    CMOS static RAM? I just did a quick google search, and here's something:
    Here's a search page:
    And here's some other stuff:

    I was also thinking: what kind of and size of chips are you using now?

  4. Terry Given

    Terry Given Guest

    BTDT, for a friend many years ago (I used my PC to record the sound). I
    clocked it with a 555, with a frequency control pot.
    last time I programmed a 1Mx8 EPROM it took a few 10s of seconds. look up
    quick-charging algorithms.
    You can use DRAMs the easy way - with a microcontroller. DIY muxing,
    refreshing - just re-arrange rows and columns such that reading the low 2^n
    bytes refreshes the whole ram. I have done this myself, after pinching the
    idea from an Elektor printer buffer design in the late 80s.

  5. Tim Porter

    Tim Porter Guest

    The 'play only' version I built uses a 27x512 EPROM.
    If I use 8khz sample rate it'll hold 8 seconds of audio.

    Thanks to everyone who offered pointers for my project, I like the
    look of SRAM now, and a 1M chip is around £7 here, so thats fine.

  6. Rich Grise

    Rich Grise Guest

    FWIW, I just picked up a Panasonic IC recorder for about $50 at Fry's.
    It claims it will record up to 8 hrs 10 min!

    Good Luck!
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