Arranging 74151's into multiplexers

Discussion in 'Homework Help' started by kieran, May 14, 2010.

  1. kieran

    Thread Starter New Member

    May 14, 2010
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    Hey there

    I am knew to electronic's and this website so this question might sound super dumb. I have to arrange several 74151 1-of-8 multiplevers to form a 1-of-64 mulitplexer. Now assuming the word several means a few, i think i have to have 8 1-of8 multiplexers, and connect each output to a 9th 74151 multiplexer, to effectively give me a 1-of-64. is this correct. A fellow IT mate disagree's and thinks its impossible to do with a 74151 rather a 74157, but this is what the quesiton asks.

    Thanks very much

    Kieran
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Do you have a schematic?
     
  3. kieran

    Thread Starter New Member

    May 14, 2010
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    Na mate i wish i did but all it says is "Arrange several 74151 1-of-8 multiplexers to form a 1-of64 multiplexer". So all i can think of is to have 8 and join all the output's to another 1-of-8 to theoreticall make a 1-of-64 multiplexer
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Not quite. Each '151 has three selection lines and an enable. That's a big hint.
     
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  5. kieran

    Thread Starter New Member

    May 14, 2010
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    Thanks beenthere. I think i understand what your saying, but i don't know how to implement it. I will still need 8 multiplexers to get 64, but i don't think i will need the 9th. If place an inverter on E3 of my circuit and leave E1 and E2 as the appear standard (if that makes sense). And have all of them connected to A0, A1, and A2, and change me E's to suit (1st '151' has E1 and E2, second '151' had E2 and E3 etc). Then i should have a 1-64 multiplexer. Is this right or am i just confusing people?
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    You will use the 9th to control the 8 that will give you the 64 inputs.

    You need 1 to control the 8.
     
    Last edited: May 15, 2010
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    It might be better to say "use one to pass the output of the active '151".

    However it is stated, the OP needs to make a schematic that at least shows the enabling circuitry.
     
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  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    Agreed on both points. The wording and the need for a schematic.
     
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  9. kieran

    Thread Starter New Member

    May 14, 2010
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    Choice thanks guys. Well i will attempt to draw a circuit/schematic and get back you. Hopefully it will make sense. I think i have a good idea now. Keep up the good work
     
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