Homework problem: Complete the table for the following sequential circuit.

Discussion in 'Homework Help' started by Gonzalo Armbrust, Jun 28, 2015.

  1. Gonzalo Armbrust

    Thread Starter New Member

    Jun 28, 2015
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    I have to construct a truth table based on the sequential circuit that is given, however i'm incredibly lost as to where to start. ( I have attached a picture of the problem below)

    For these types of problems, am I able to start at any input?For example according to the problem, lets say that A=0, B=0, and =1, if I know that B is set to zero, which then gets negated by the NOT gate to 1, and combined with X ( which equals 1), then the output of the logic gate is 1 ( since the output of the gate negated is 1), does this make the next state of A = 1, and also B = 1, since it would still be 1 through the D circuit?

    OR

    to find the next state value of B, could I just start at A input, and deduce it would be the same value of what A is initially since they are only seperated by a D circuit?

    My biggest question for these types of questions is, what input do I start exactly?
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Start with the top of the Truth Table and sequentially solve for each state until you reach the bottom.
     
  3. Gonzalo Armbrust

    Thread Starter New Member

    Jun 28, 2015
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    I worked through it, and this is the truth table I came up with, is this correct?
     
  4. tshuck

    Well-Known Member

    Oct 18, 2012
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    No. Your first row shows that 0 xor 1 is 0.

    Edit: disregard, I mistook the XNOR for XOR.
     
    Last edited: Jun 29, 2015
  5. WBahn

    Moderator

    Mar 31, 2012
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    No need for 1.1 MB files when <22KB will do quite nicely.

    HW1.jpg

    Yes, your truth table is correct.

    Notice that an XNOR gate with one input negated IS an XOR gate.
     
  6. WBahn

    Moderator

    Mar 31, 2012
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    Huh?

    It shows that, for B=0 and X=0, the (B') XNOR (X) is equal to 0.
     
  7. tshuck

    Well-Known Member

    Oct 18, 2012
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    Whoops, my mistake, I didn't realize it was XNOR. That's what I get for trying to check in while in the middle of another task.:oops:
     
  8. WBahn

    Moderator

    Mar 31, 2012
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    Know the feeling -- I'm a lousy multitasker.
     
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