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Data write/read and peak detector animation

Discussion in 'Electronic Design' started by Tom Del Rosso, Aug 4, 2012.

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  1. http://www.grc.com/animation.htm

    Comments?

    I know, the read head should be magneto-resistive instead of inductive.

    But should it be Differential Manchester? The square wave transitions are
    not encoded like this:

    http://en.wikipedia.org/wiki/Differential_Manchester_encoding


    For some people the most interesting thing is that the animation is coded in
    javascript, with no flash or similar, and it's neatly hand-coded and
    commented, so you might want to save the source for future reference.
     
  2. Jasen Betts

    Jasen Betts Guest

    Very nice!
    Inductive is oldschool. but not wrong.
    I think It should be some sort of RLL, differential manchester is
    extremely oldschool.
    No crosspost to comp.lang.javascript :)

    Your code?

    The author has left the mouse coordinates display turned on
    in the lower right corner. (when I put debug code in javascript I
    use a hidden activation method eg: enable it with a key value in
    location.hash or location.hostname)

    The doctype is wrong, the document is not HTML4.01 Transitional.
     
  3. I should have. They would like it.

    Oh no, I didn't know it was possible with javascript until I saw that.
     
  4. Rod Speed

    Rod Speed Guest

    That’s a very superficial/dumbed down view of what actually happens.
    Yeah, its quite elegantly done.
     
  5. Jasen Betts

    Jasen Betts Guest

    A few years ago someone showed me this: (or something very similar)

    http://www.elizium.nu/scripts/lemmings/
     
  6. I was thinking in terms of a balanced signal, then realized the encoding
    didn't have to be balanced.
     
  7. Arno

    Arno Guest

    Inductive is very historic.
    Manchester is also historic. All modern drives use some PRML
    decoding, i.e. the signal is read analog and the decoding
    and error correction coding takes that into account. The
    encoding itself is also a lot more sophisticated than in
    the old RLL or MFM days.
    Not really. Unless you are trying to fix a very old tape data
    recorder, this animation is irrelevant today.

    Arno
     
  8. Manchester produces a balanced signal. That's what I was thinking of.
    Balance isn't needed for this apparently.

    I meant for those who write javascript. It's ability to do this was a
    revelation to me.

    The author's purpose was to explain something about Spinrite, the old disk
    tool. He claims it does more thorough testing than a long self test. I
    doubt it, but he is a good programmer. I told him recently he should put
    that talent to use on a new product, but people still buy Spinrite. It has
    a following, like fans.
     
  9. Arno

    Arno Guest

    Oh, I see. That is actually interesting. Agreed.
    And it is completely bogus today, basically a scam. Hence
    my negative reaction to it. As modern disks and controllers
    do not offer the interface MFM and RLL drives offered (you
    could do a raw digital reading of the data). The equivalent is
    not even possible today without uploading specialized firmware
    to the drive or using secret vendor functionality. There
    certainly is no standardized interface for asking the drive
    to give you the analog signal. And the on-disk encoding is
    also not standardized. SpinRite would need both to do any
    better than a long selftest.

    With MFM/RLL that was all different, and SpinRite did indeed
    do better. These days are over, but the SpinRite fans
    do not understand that. They just want their "god" tool
    and feel superiour.

    Arno
     
  10. Tim Williams

    Tim Williams Guest

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