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TTL - Is there a logic gate or IC that does this?

  1. Jun 5, 2014 #1
    So this summer I plan on taking a long break from my arduino and learning some more 'ancient' and fun stuff. I plan on learning to use and make different circuits using TTL's. I have read a bit on it and learned on the basic logic gates like(using '/' as separator for the reverse) n/and,n/or. There is one kind of logic gate I'm curious about(this is something I've made on minecraft and if it works irl with logic gates). Question:

    Is there a logic gate or IC that (uses 2 inputs and 2 outputs) when line A is high, line B will never be(and reverse). No matter what you put into line (off), if will produce no output.

    This would be a really useful piece for my first project I am planning for the summer. I plan on making a battery powered Tic Tac Toe game. I haven't started yet and am going to start drawing up a sheet(don't remember what they are called, it's a drawing on how the entire thing is connected and where) for what I am going to build.
    Last edited: Jun 5, 2014
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  3. Jun 5, 2014 #2

    Simon Bridge

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    Please show us the truth table for the device you are trying to describe.
  4. Jun 5, 2014 #3
    A= wire 1
    B= wire 2
    C= which was active first

    A B C | OutPut-A output-B
    1 0 A| 1 0
    1 1 A| 1 0
    0 0 0| 0 0
    0 1 B| 0 1
    1 1 B| 0 1

    I have not made a truth table before, so This may be a little rough
  5. Jun 5, 2014 #4


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    TTL is very high power.
    Direct CMOS equivalents to TTL gates are available in the 74HCxx series.

    I would strongly suggest you experiment with low power 4000 series CMOS rather than TTL gates.
  6. Jun 5, 2014 #5


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  7. Jun 5, 2014 #6
    I don't think a flip-flop really suits his purpose. Or at least not by itself. He wants two separate outputs(I assume to drive different color LEDs), not a Q and Q'.

    Considering you want to make a Tic-Tac-Toe game, I think you are best off doing the whole thing in code. Handling resets will be much easier. If you really wanted to use discrete logic gates, you could combine flip-flops with tri-state buffers. But I don't know of a simple logic device that does what you are looking for.
  8. Jun 5, 2014 #7
    I want to break away from my arduino and learn more off hand stuff so I don't spend as much time and memory on my arduino
  9. Jun 5, 2014 #8
    This statement "C= which was active first" does not make a lot of sense in logic like this - do you mean " the input that went high (1) first" or " the one that changed state first" -- these inputs are not "active" they are always 0 or 1 -- both states are equivalently "active".
  10. Jun 5, 2014 #9
    Sorry, it does sound unusual and not right, I did mean High/1.
  11. Jun 5, 2014 #10


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    Hmm. I started my "ancient' logic learning with RTL. :approve:
  12. Jun 5, 2014 #11


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    I still use RTL...

    A simple RS Flip/Flop made from NAND gates with output inverters will satisfy the logic table presented.
    See attached.

    Attached Files:

  13. Jun 5, 2014 #12
    I may be a bit confused,but a nand gate sends a 1 as long as there is a 1 on an input. The diagram(above), how I am reading it is that as long as one is 1, the other will also return a 1(which I am looking for a reverse where if one is 1, the other will always return a 0)

    This is where I looked up nand logic gate btw. http://en.m.wikipedia.org/wiki/NAND_logic
  14. Jun 5, 2014 #13
    A NAND gate sends 1 except when both inputs are 1.

    With 00 as inputs, the two NAND gates both send 1. When input goes to 1, the corresponding NAND gate goes to 0, which keeps the other NAND gate at 1 regardless of what the other input does.
  15. Jun 5, 2014 #14
    Sorry, I'm probably getting confused somewhere. I keep seeing this and see that nand lets there be a 0 when there is both inputs 1. Am messing myself up somewhere? ImageUploadedByPhysics Forums1402013482.345354.jpg
  16. Jun 5, 2014 #15
    thats right. did you forget about the inverting gates at the end of Baluncore's circuit?
  17. Jun 5, 2014 #16
    Ok, I have not seen that symbol before (and I took a huge step when asking this question), but I'm guessing the diode triangle with open ball inverts a 1 making it a 0 instead?
  18. Jun 5, 2014 #17

    Simon Bridge

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    Niggle: A diode symbol is a triangle with a bar across the output point.

    A triangle by itself, with only two leads, is a "buffer" or a "yes gate"
    ... the output is logically the same as the input. H>H, L>L.

    An open circle on the output of any gate inverts the output - i.e. a nand gate symbol is an and gate with an open circle on the end.

    Thus a buffer with an open circle takes the input and returns the opposite... as you have correctly surmised.
    This is called an "inverter" or a "not gate".
  19. Jun 5, 2014 #18
    So when the inverter get a 0, does it pull electricity from a Separate line to invert that 0 to a 1?
  20. Jun 5, 2014 #19
    all the logic gates do. Those symbols are an abstraction.
  21. Jun 5, 2014 #20
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