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Determining a non-periodic digital timing scheme?

Discussion in 'Electronic Design' started by JeffC, Jan 31, 2007.

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  1. JeffC

    JeffC Guest

    I have a piece of equipment (DLP projector) for which I am trying to
    construct a digital timing diagram. The digital signals this device
    uses are globally periodic (generally over several milliseconds) but
    aperiodic over a short time interval(ns to us). That is to say the
    waveform eventually repeats itself but is not repetitive over a short
    time interval. And so I can't get my scope (Tektronics) to produce a
    stable waveform for analysis. Taking a single time sequence is not
    particularly helpful as the record length of the scope is still only a
    fraction of the global period. Does anyone have any tips on how to deal
    with this problem? Thanks!
     
  2. Guest

    Other than a storage scope? If you are just looking at timing, then a
    scope is overkill. You could store more information with a logic
    analyzer. I've worked at places (but haven't done this first hand)
    where the logic analyzer was used as a high speed frame buffer prior
    to analysis on a PC. We did that for flash data converters in the lab.
     
  3. You want to readout the timing in detail ? Attach an
    FPGA and decode the signal to a parallel or logical
    form, then grab the parallel/logical stream.

    Rene
     
  4. Guest


    1) It's spelled Tektronix. It's a pet peeve of mine but has let me
    snag some cheap stuff on eBay.
    2) You need a logic analyzer, sounds like a scope is just about the
    worst tool for what you want.
    http://www.pctestinstruments.com/
     
  5. neon

    neon

    1,325
    0
    Oct 21, 2006
    Wrong scope try memory scopes. Digital analizers are not real time devices but close to it.
     
  6. JeffC

    JeffC Guest

    Thanks for all the replies. The INTRONIX LA1034
    (pctestinstruments.com)looks ideal with the exception of the 2k sample
    limit which may be too short for my purposes.
     
  7. Guest

    You can buy real logic analyzers (old HP boxes) quite cheap if you
    don't need speed. Just make sure to get the pods with the analyzer.
    For instance:
    http://cgi.ebay.com/HP-16500B-LOGIC...2QQihZ011QQcategoryZ97186QQrdZ1QQcmdZViewItem
    Those analyzers on ebay without pods are really boat anchors.

    There may be more inputs than you need, so sometimes you can play
    games with external logic to increase the length of the sequence
    stored. For instance, you can build logic to store two samples, then
    feed them in parallel to the logic analyzer, effectively doubling the
    length of the sequence. When we were testing flash converters, the
    logic analyzer wasn't fast enough to process the data, but the data
    was paired two bytes at a time, then fed to 16 lines into the
    analyzer.
     
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