3.4.2. Verilog Example: 4-Bit Binary Adder

Try these first

1. 1.

   What is the purpose of a 4-bit binary adder?

   Hint

   Think about the basic function of addition.

2. 2.

   What are the inputs of the ADER_4BIT module?

   Hint

   Consider what you need to add two numbers.

3. 3.

   What is the function of the carry-out (Cout) in a 4-bit binary adder?

   • To hold the sum
   • To indicate overflow
   • To represent input carry

   Hint

   Think of when binary addition results in a value greater than 15.

4. 4.

   True or False: The line of code assign {Cout, Sum} = A + B + Cin; can only handle 8-bit outputs.

   • True
   • False

   Hint

   Review what is being added in this line.

5. 5.

   Can you modify the 4-bit adder to include an optional carry in from a previous low bit adder and explain how the implementation would change?

   Hint

   Reflect on how carry propagation works in multi-bit addition.

6. 6.

   Design a Verilog module for a 4-bit binary subtractor using similar principles to the 4-bit adder.

   Hint

   Think of how you would reverse the addition process.