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Parallele port buffering question ....

Discussion in 'Electronic Basics' started by rgb, Sep 11, 2003.

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  1. rgb

    rgb Guest


    As a newbie I was wondering if it gonna smoke ;-)

    I'm planning to use a 74LS244 to bridge between a standard paralelle
    port and breadboard (use for prototype of LS IC).

    Is it safe, I mean will it stop bad stuff from prototype side to go to
    pararallel port ics ?

    And also what will happen if I disable output of LS244
    I mean how will react standard LS TTL to HiZ input ?


    Thanks :)
  2. Optoisolators would be the safest bet...
  3. rgb wrote:
    An open circuit (high Z) is a logic high to any TTL input. Not a very
    noise immune high, but a functional high.
  4. CFoley1064

    CFoley1064 Guest

    Since you're a newbie, your first piece of advice should be to use a parallel
    port on a plug-in ISA card on the computer you were going to throw away, anyway
    (at least for the prototyping stage). Parallel ports on motherboards
    (especially laptop motherboards) are fairly time consuming and/or expensive to
    fix. But if you've got a dozen "throwaway" ISA I/O cards which happen to have
    an LPT2 on them, you don't have to worry too much about smoke -- they're
    recycled, anyway.

    Look at Jan Axelson's website for plenty of information and links
    on parallel port interfacing. Or better yet, buy the Axelson book, "Parallel
    Port Complete", which has everything you need, including software examples in
    just about every programming language.

    Good luck.
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