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JK flip flop suggestions?

  1. Oct 29, 2012 #1
    Hi, I am looking to build some very simple state machines, with JK flip flops. I am planning to run them off a 9 volt battery, if that is feasible.

    Does anyone have a suggestion on what JK flip flop to buy, preferably from Mouser?
    I know Mouser has about 300 different parameters to pick from, I just want someone to suggest a good starting JK. I am not going to be doing anything high power, or fast frequency switching. I believe I am going to want a positive trigger though.

    Anyone have a good suggestion?
     
  2. jcsd
  3. Oct 29, 2012 #2
    Type 4027 or HEF4027/CD4027
     
  4. Nov 2, 2012 #3
    JK flip-flops are old-fashioned. D latches and D flip-flops cover about all uses and have replaced all others. It would need a very special need and tricky circuitry to justify a JK.

    Plus, a state machine traditionally uses D flip-flops, with logic between. Anything else is probably too complicated to design.
     
  5. Nov 5, 2012 #4
    D-flip flops still have a clock input for them to change states, right?
    Do you have any suggestions for a D-flip flop?
     
  6. Nov 5, 2012 #5

    uart

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    Yes and they're much easier to design with as the "next state" is simply "D". (So no need to mess about with translating "next states" into equations for J and K).

    And as long as you are sticking with purely synchronous designs (all f/flops having common clock) then hex and octal D flipflop packages are readily available.

    As Enthalpy said, JK flipflops are pretty outdated. Well actually any random SSI logic implementation is going to be outdated, but it's probably still a very good "hands on" learning experience for familiarizing yourself with logic design.

    The basic idea behind J-K was that some of the next state logic could (if you were lucky) be shoehorned into the J-k functionality, thereby perhaps saving a gate or two in the combination logic. You'll probably get a bigger saving however by just making use of the good number of D f/flops (8) that you can get in a single SSI IC, and then just using an all nand combinatorial logic.

    74xx273 is an octal edge triggered D flipflop with a reset line (so good for forcing a well defined initial state). The "xx" in this code represents the exact logic family. Eg 74HC273 is the part in the "HC" (5 volt high performance cmos) logic family, probably one of the more readily available types.
     
    Last edited: Nov 5, 2012
  7. Nov 5, 2012 #6
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