DOB seven segment display

Discussion in 'Homework Help' started by axel1111, Apr 20, 2011.

  1. axel1111

    Thread Starter New Member

    Apr 20, 2011
    2
    0
    iam getting confused on this problem in my homework in which all you have to do is display your DOB on 1 seven segment display by cycleing through them with three switches in binary. I am getting stuck at where it says "write the simplified Sum-Of-Products Boolean equations forthe seven outputs a, b, c, d, e, f, & g."

    My truth table is here:http://pastebin.com/UuKatSvZ

    (using pastebin so everything is still inline)

    so my question is how would i write out the SOP equation for a,b,c,d,e,f & g?
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Actually, you need 7 Boolean functions, one for each segment of the 7-segment display. Each function will correspond to a logic circuit that will read the three inputs and drive only one segment.

    Do you know how to construct a Boolean function from a truth table through a Karnaugh map? Check here if the answer is no: http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Logic/Logic3.html
     
  3. axel1111

    Thread Starter New Member

    Apr 20, 2011
    2
    0
    i know how to make a boolean expression from a kmap but this one doesnt make any sense to me
     
  4. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Ok, let's describe it in a different way:

    We know that the 7-seg display must show a predefined symbol for each different combination of its 3-bit input.
    We 'll take it a bit further and say that each separate segment must be either ON or OFF for each of the 8 different inputs. Isn't that a standart boolean function that takes the value 0 or 1 depending on 3 input variables X, Y and Z?
    And since we have 7 segment, we have 7 boolean functions in our hands.
    For each function, a digital circuit must be built in order to drive the respective segment.

    I 'll give you the example of the "a" segment, based on your image attachment:
    Let the function A represent the boolean function that will describe the operation of the "a" segment.
    A(X,Y,Z)=Σ(2,5).
    After the simplification (which in this case is non-existent), that becomes:
    A=X'YZ'+XY'Z.
    That is the function which after being implemented into a circuit, will drive the "a" segment.

    Is that clear?
     
Loading...