Discussion in 'Homework Help' started by ahmed elaraby, Jul 8, 2011.

  1. ahmed elaraby

    Thread Starter New Member

    Jul 8, 2011
    i want to make 4-bit Arithematics Logic Unit (ALU)
    don't use any full IC (using logic gates only)
    I want idea for this design please
    4 bit ALU able to generate the following four flag (i want to know what the meaning of flag):
    a-carry/borrow flag to be set on carry (addition) or borrow (subtraction) operations
    b-sign flag to be set when the resulting number is negative (2's complement only)
    c-zero flag to be set if the resulting number is zero
    d-overflow flag to be set if the two most significant carry outputs are not equal
    i need help plz!!!!!
  2. simo_x


    Dec 23, 2010
    If I am not wrong, if you know the number of inputs & outputs, you should be able to do it with flip flops.
    Just applying the principles of digital electronics.
  3. bertus


    Apr 5, 2008
  4. MrCarlos

    Active Member

    Jan 2, 2010
    Hello ahmed Elaraby

    An ALU requires:
    4-BIT's to say what function to execute.
    4-BIT's to the operand "A".
    4-BIT's to the operand "B".
    4-BIT's to show the function result.

    You say: (i want to know what The Meaning of flag):
    Flag is a sign: audible, visual, sensory announcing an event which must be notified.
    Audible buzzer.
    Visual: LED.
    Sensitive: a tap on the shoulder.

    In the case of ALU is
    A BIT to indicate the carry / borrow.
    A BIT for displaying the sign.
    A BIT to indicate zero.
    A BIT to signal the overflow.

    Over here there's someone else asking for help about the ALU. Visit this link: # post378078

    at your service