<<< Adding Signed Numbers     Index     Adding the Sign Bits >>>

6. The Full Adder Truth Table

  • Recall the truth table for the 2's complement full adder logic:

     

    INPUTS OUTPUTS
    A B CARRY IN CARRY OUT SUM
    0 0 0 0 0
    0 0 1 0 1
    0 1 0 0 1
    0 1 1 1 0
    1 0 0 0 1
    1 0 1 1 0
    1 1 0 1 0
    1 1 1 1 1

     

  •  

     

  • The truth table includes five columns with three inputs and two outputs.

    1. input A

    2. input B

    3. carry IN for the current column

    4. resulting carry OUT (carry-over), generated for the next column

    5. the resulting SUM.

<<< Adding Signed Numbers     Index     Adding the Sign Bits >>>