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Rise and fall time of TI 'F' family

Discussion in 'Electronic Basics' started by [email protected], Jul 13, 2005.

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  1. Guest

    I am making a high speed digital system board which will demonstrate
    the pitfalls of high speed design, as part of a final project.
    I am using a TI's F family to give me small rise and fall times to
    demonstrate transmission line effects. However, I cant find the rise
    and fall times of their F family anywhere. Does anyone know what it is
    or better send me the datasheet where it is specified.

  2. John Fields

    John Fields Guest

    Go to:

    Search for the part number you have in mind, navigate to the data
    sheet, and read it.
  3. Kunal

    Kunal Guest

    Goto yourself.
    Pick the 74F175 datasheet or any other F chip and see that only the
    propagation delay is specified.

  4. John  Larkin

    John Larkin Guest

    I have a National databook that cites their FAST as having Tr of
    1.8-2.8 ns, and Tf of 1.6-2.6 ns.

    Some of the TinyLogic cmos parts are well under 1 ns.

  5. PeteS

    PeteS Guest

    Of course, if you want to see where those pitfalls can **really** hurt
    you, go to

    (I'm one of the contributing authors of the spec :)


  6. John Larkin

    John Larkin Guest

    How much of channel-based i/o, do you think, is based on the bloat of
    Windows? People are putting stuff like tcp/ip stacks in hardware these
    days; what's next? Word could sure use some hardware assist!

    IBM's Cell thing is sort of the ultimate architecture... a processor
    per process. That would result in interesting OS architectures.

    Funny: I went to the Semi show on Tuesday. Microsoft had a big display
    featuring a Microsoft-automated Hummer3 (which looks like a
    horizontally-stretched SUV... really dumb looking) and I joked to a
    guy about where were the ctrl/alt/delete buttons. He replied that
    they'd been trying to boot it up all morning, no luck so far. And
    they're pushing XpEmbedded for wafer fabs!

  7. Kunal

    Kunal Guest

    Thanks John. Ill use the 2.8ns seconds for my calculations. That would
    be the 'worst' case for me.
    I am making a SI demo board with 5 experiments
    1) Transmission line effects : See ringing/reflections on long traces
    and how terminations reduce that
    2) Crosstalk
    3) Power Integrity : heavy loads connected to a DIP package with a thin
    long trace to the power rails
    4) Metastability : Straight out of Howard Johnson's book
    5) Multi-drop bus : SHow how heavily loading an output can slow rise
    time due to caps, thus reduce system freq.

    My main problem is that I have to be able to see all these effects on a
    100MHz scope (Tr = 3.5ns). I used howard johnson's 21:1 probe
    configuration (in his book), lets hope it works out.
  8. John  Larkin

    John Larkin Guest

    Maybe include an LS flipflop. They're notorious for metastability and
    are slow enough that your scope could catch them. I've heard of an
    LS74 oscillating for a microsecond if properly teased, and making
    audible clocks on an FM radio every time is went metastable.

  9. Fred Abse

    Fred Abse Guest

  10. Joerg

    Joerg Guest

    Hello John,
    At least there is a clear quality indicator for cars after they have
    been in production for a while (sometimes even if they haven't): The
    quality and reliability is inversely proportional to the cost of the
    extended warranty. That rule hasn't failed me since my college days.

    Regards, Joerg
  11. Bob Stephens

    Bob Stephens Guest

    That's a pretty good one.

  12. Joerg

    Joerg Guest

    Hello Bob,
    When I bought my first "real" car I had one more: I picked a few models
    that fit my needs. Then I went to the dealers of each brand and,
    pretending I already had one, asked for the price of a spare part. The
    left mirror, since that gets clipped a lot. BIG differences. Then I went
    ahead and bought the car where this part had the most reasonable price.

    Oh, and the company that made the mirrors was close to where I lived. So
    I knew what these mirrors cost. They were all in the same ball park.

    Regards, Joerg
  13. Ken Smith

    Ken Smith Guest

    Remember the "transputer" with many ALUs for a single task. Now If IBM
    would just make a multiple version of a chip like that so that each thread
    in XP could have thousands of ALUs to work on it, a 3GHz machine might be
    able to keep up with RS232 data coming from an 8051. That would be nice
    wouldn't it.
  14. Bob Monsen

    Bob Monsen Guest

    You sound bitter... ;)

    I just upgraded my sister in law to 512 MB of memory, so she can surf
    the web. She was running 128 MB, and XP SP2 was SO SLOW that she simply
    could not do anything. After upgrading, the system was zippy.

    Same situation for a neighbor of mine, who, in addition to having over
    600 bits and pieces of spyware and a rootkit trojan on the system, was
    running McAfee Internet Security. After I reformatted her disk,
    reinstalled everything, and upgraded to SP2, her 128 MB system was quite
    slow. Turns out McAfee sucks up about 50% of the cpu just sitting there,
    according to Task Manager. McAfee is actually worse than having the
    trojan; at least the trojan was free.

    Now, my first home computer was a 128K (not M, K) mac. At work, I had
    used minicomputers with a maximum address space of 2 MB, that supported
    compiles for 20 users.

    My suspicion is that microsoft made a deal with compact, dell, etc, at
    some point in the past (probably when they were killing off OS/2) that
    guaranteed that if the mfgrs sold dos/windows, and made it hard to get
    anything else, then MS would make the OS would bloat so badly, and
    perform so miserably, that people would be required to constantly
    upgrade their computers to get the same performance they used to get.

    (whatever happened to the connection machine? The BBN butterfly
    architecture? All of that massively parallel stuff has fallen by the
    wayside, probably in favor of massively parallel stuff built on racks of
    hundreds of cheap PCs, running Linux.)

    Bob Monsen

    If a little knowledge is dangerous, where is the man who has
    so much as to be out of danger?
    Thomas Henry Huxley, 1877
  15. Joerg

    Joerg Guest

    Hello Bob,
    My father worked on the design of a system that had 2K of memory and
    controlled a complete cold-rolled steel production line. IIRC it never
    crashed. Probably around the time Bill Gates was in first grade.
    One technique is simply not to upgrade. I am writing this on what some
    would consider a clunker. Pentium 2, 64MB of RAM, old NT. Mozilla seems
    to have some memory leaks so once in a while I have to re-start and it
    speeds up again. But not more often than once a day. You can kind of see
    when it's time because it starts grinding on the hard disk page file too
    much. This is the machine I use to keep online data sheets on screen
    while designing on the other PC.

    I just don't follow the bloat unless there is a very compelling reason.
    The only reason I can think of is if some SW isn't backwards compatible.
    However, I tend not to buy such SW so only a client requirement could
    trigger that situation.

    Regards, Joerg
  16. Guy Macon

    Guy Macon Guest

    This can work well, but not if you are using a Microsoft OS and are
    not behind a standalone firewall. The good news is that FREESCO
    running on an old 486 makes a great firewall.
  17. I have no idea how much memory it had, but the TV event switching
    computer we used when I first started in broadcasting in 1980 used
    about a 15 or 20 foot length of ticker tape to load its operating

    It was replaced in 1987 or so with an XT with 256k of RAM. Only 256k
    was enabled, I later discovered from examining the silkscreen on the
    board, so I righted that wrong, and upped it to the full 640k that was
    actually there. No difference in performance that I could tell. :)

  18. Guest

    Even better is to upgrade hardware but not OS. 98 is still ok, and is
    quick on a modern PC. I mean why pay MS yet again for something thats
    only going to cripple your work output?

    Nother approach is to have 2 sets of each app, one full featured and
    the other a quick version. Only use the full bloat version when its
    needed, most of time use the quickie. Makes the whole business miles

  19. Guest

    I'd like to upgrade mine too... How do you open the head? Does the port
    labelled 'mouth' take CD or DVD? what are those ear connectors for?

    I've been trying the nose connectors, but there seem to be
    compatibility issues, the system refuses to accept any of the nose
    plugins I've tried, even though they fit correctly. What am I doing

    Once a day scan is a more sensible setting, unless in a hostile
    situation. Scanning every file every time does cane performance.

    That certainly is the game, or part of it, though theres no deal
    needed. MS builds in more features to impress buyers: these features
    mean more code which means slower, and that means constant upgrading of
    hardware. Sometimes its worth it, eg the move from 3.1 to 95. Sometimes
    its not, eg xp.

    And why do the hardware sellers push MS? Because its what will bring
    the customer back in 1-2 years for another system. And another, and

    MS has tried making deals that hardware vendors only sell MS OSes or
    else MS wont sell them Win, but IIRC it was ruled illegal.

    If you dont want to play that game, stick with an older less bloated OS
    and non bloated apps.

  20. Joerg

    Joerg Guest

    Hello NT,
    Better yet try to live with the simple things. I run my whole business
    accounting on MS-Works database. It works like a champ, is simple and
    fast. Then I use Works spreadsheet for EE math and other fancy stuff. It
    is amazing what you can do with a $100 software that often even comes
    free with a new PC.

    Regards, Joerg
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