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Circuit minimization

Discussion in 'Electronic Basics' started by James, May 15, 2004.

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  1. James

    James Guest

    I have a circuit that I've minimized using two different methods that have
    produced two different answers.

    The circuit is (A(B+C))+(A'BC')

    Which I then expanded to disjunctive form:


    Using a Karnaugh map I got the expression minimized to AB+AC+BC'

    However using Venn diagrams I got the circuit minimized to AC+BC'

    The thing I don't understand is that I thought Karnaugh maps always produced
    a completely minimized circuit so what is it I'm doing wrong?
  2. Jim Thompson

    Jim Thompson Guest

    Your Karnaugh map solution is correct. You erred somewhere in the
    Venn diagram. Maybe you left out the "don't care" states?

    ...Jim Thompson
  3. James

    James Guest

    You know, I've just looked over it again and it appears the Karnaugh map
    solution is actually *wrong*.

    I used three circles when I only need to use two.
  4. Fred Bloggs

    Fred Bloggs Guest

    It is wrong- you have AB + AC +A'BC' so that AB term expands to ABC+ABC'
    obviously- then the ABC+AC=AC obviously, and the
    ABC'+A'BC'=(A+A')BC'=BC' so that the finished expression is AC+BC'.
  5. Fred Bloggs

    Fred Bloggs Guest

    See- I warned you about that pill....
  6. Soeren

    Soeren Guest

    Hi James,

    You need all 3 circles to avoid race hazard.
  7. Jim Thompson

    Jim Thompson Guest

    Ehhhh? I think it's YOU that needs to check his pills ;-)

    ...Jim Thompson
  8. Fred Bloggs

    Fred Bloggs Guest

    LOL!!- The only pills I take are an occasional vitamin-C....:)
  9. John Larkin

    John Larkin Guest

    Do some Bs, too. They're really good for you.

  10. Michael

    Michael Guest

    No, not wrong. Just not minimal. Apparently you did use "three
    circles". Only two are required. Your third term, AB, is included
    within the other two, (AC + BC').
  11. Jim Thompson

    Jim Thompson Guest

    Are you still saying that BC' + AC + AB is not correct? <Big Frown>

    Better double-up on the vitamin-C ;-)

    ...Jim Thompson
  12. Jim Thompson

    Jim Thompson Guest

    Aha! Missed that :-(

    ...Jim Thompson
  13. Jim Thompson

    Jim Thompson Guest

    Nevermind! Duh! I overlooked minimal :-(

    I'll plead that it was a pill problem ;-)

    Doc took me off of Atenolol on Friday since it wasn't controlling my
    BP and put me on atacand HCT.

    Saturday night had a rebound effect from going off of Atenolol and
    went tachycardia (100 BPS).

    Added back in 1/2 dose of Atenolol and will wean slowly.

    Everything seems OK now.

    ...Jim Thompson
  14. Soeren

    Soeren Guest

    Hi Michael,

    Yes, but there is a risk of race hazard between ABCD and AB'CD which will
    need at least a circle around ABD and to minimize that, you go for the
    entire column which gives AB, making it AB+AC+BC' - if it to be used in
    the real world.
  15. Michael

    Michael Guest

    Don't beat yourself up too bad, Jim. I had to actually map both
    (AB+AC+BC') and (AC+BC') to see whuddup wi' with the first.
  16. Michael

    Michael Guest

    Naw, not really. Here we always interpose a latch between combinatorial
    and down-stream stuff. :)
  17. Jim Thompson

    Jim Thompson Guest

    I was using KarnaughMap v4.4.5, but didn't trust it, and also did a
    hand check before I fessed up ;-)

    ...Jim Thompson
  18. John Larkin

    John Larkin Guest

    My doctor (a very nice Chinese lady) put me on Atenolol. It's a beta
    blocker and makes bp go down by reducing heart output. That made me
    get so easily winded that I couldn't get any decent exercize, which
    makes one get fat, raising bp! Not good to mess with your heart!

    Now I'm taking cheap stuff, an ace inhibitor and a diuretic, and they
    work great for me. I tune the dosage to just below the point when I
    fall over getting out of a chair or bed. 115/75 is easy, with a little
    exercize and weight control. Some MDs think everybody over 45 should
    take these routinely, along with aspirin and a statin.

    This is relevant to electronic design: older people have the tricks
    and experience (and just plain balls) to do great design, but they
    have to stay in tune, not to mention alive, to keep their brains
    working at top form. I know too many engineers who have gotten fat and
    lazy, and mostly sleep at their desks in the afternoon.


    back to hacking this uP code. Some days, like today, I seem to break
    everything I touch. This keypad thing - membrane switch, up/down the
    menu list, variable jogging, typematic, title flashing, special error
    messages with timeouts, raw 16-segment VF drive - is getting hairy.
    Time to test the latest pass.


    P = 1000h ; FH L KB
    D = 0008h ; F H L K B
    R = 2000h ; F H L K B
    C = 0004h ; F H L K B
    H = 0080h ; F H L K B
    K = 0100h ; F HLK B
    L = 0200h ; GGGGGGG MMMMMMM
    A = 0001h ; E RPN C
    B = 0002h ; E R P N C
    F = 0020h ; E R P N C
    G = 0040h ; E R P N C
    M = 0400h ; E R P N C
    E = 0010h ; ER P NC
  19. Jim Thompson

    Jim Thompson Guest

    Same here... put on weight (about 25#) since going on Atenolol. So I
    finally confronted the doc about it last Friday. She switched me to
    atacand HCT, but neglected to consider that you need to wind down from
    the Atenolol, otherwise your heart goes bananas and ups the rate
    precipitously :-(
    IMHO statins SUCK... they're destructive of muscle tissue. Just eat a
    handful of walnuts daily.
    I don't have a falling asleep problem, but I'm distinctly
    out-of-shape, and determined to get back to high-school weight ;-)

    ...Jim Thompson
  20. Where did D come from?
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