What are the boolean algebraic formula for the output of a 2-input half adder?
Carry = A . B
Sum = A XOR B
What is the difference between a half adder and a full adder?
A full adder has a Carry In in addition.
What are the boolean algeberaic formulae for the output of a full adder?
Sum = A XOR B XOR CIN
CarryOUT = A.B + A.CIN + B.CIN
Draw the symbolic box diagram for a 2 input Full Adder showing all inputs and outputs
Draw the box diagram showing how to connect full adders to add together two 4-bit numbers
How do you calculate the propagation delay for a ripple carry adder?
Draw the truth table for a full adder, mentioning carry status at each line.
How do we subtract two numbers using full adders?
A + (-B)
We take the 2's complement of B and add with A
We wary of overflow and underflow
How do we detect overflow when dealing with subtraction/ 2's complement?
Overflow if the carry out is different to the carry in
Overflow = CIN XOR COUT
Draw a 4-bit subtracter
Using XOR gates and a bitinvert signal show how you can design one circuit that can add or subtract two 4-bit numbers.