logic functions?

Discussion in 'Homework Help' started by harvez_007, Nov 8, 2008.

  1. harvez_007

    Thread Starter New Member

    May 2, 2008
    2
    0
    Hi.

    I am having heaps of trouble understanding how this works:

    ____________
    ______
    ___ __
    X = A.B + A + C ?

    How do i draw a logic circuit using this function?

    What do all the lines mean and do?

    Could you please explain it to me, that would be great :)

    Cheers.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    A' means A with the line above because i cant write it. It means that the value of A is inverted, that if A=1 then A'=0 or if A=0 then A'=1

    In the logic function it means that you put a NOT gate after the function that is inverted.
    For example, if you want the logic circuit of (AB)' you will put an AND gate and then a NOT gate on the output of the AND gate.
    If you have A', then you put a NOT gate on the output of A which is a signal from a device.

    In your case, (AB)' means that you need an AND gate (for AB) and a NOT gate on its output (to implement the inversion noted by ') which is equivalent to a NAND gate. Then you will need a 3 input OR gate, on its inputs you will connect the output of the NAND gate, the A input signal and the C input signal. Finally, to implement the inversion denoted by X' you put a NOT gate on the output of the OR gate.
     
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