## Step : **Understand Problem and Requirements**Explanation:**You are asked design and implement **4-bitder** for two numbers in **'s complement form producing a -bit **Sum and a **** output. The must use halfers (H) and fullers (F), and any out from the most bit (MSB) must be added back to the least significant bit (LSB) — this is called **end-around carry** (EAC). Deliverables include: - Circuit diagram (with clear signals and EAC) - Logic for zero detection - VHDL code (dataflow + structural modeling) - Testbench covering all cases (positive + positive, etc.), checking for zero output, and proper comments. **Key Points to Note:** - All temporary signals must be shown and labeled in both the diagram and code. - Zero output must be high when the result is exactly zero. - Testbench must cover all described combinations and check the zero case. --- ## Step 2: **Plan and Split the Solution** **Explanation:** To address the task, break it into these major components: ### 1. **Block-level or Gate-level Circuit Diagram** - Draw a circuit using 4 stages (one per bit), each using a half-adder or full-adder as required. - Clearly show all signals, including interim carries and the logic for end-around carry (carry-out from MSB loops back to carry-in on LSB). - Label all inputs (A[3:], B[3:]), outputs (Sum[3:], Zero), and all temporary signals. ### 2. **Zero Detection Logic** - Implement logic that outputs high ('1') if all bits of the sum are zero. - This can be done using a NOR gate or equivalent logic on the sum bits. ### 3. **VHDL Implementation** - Translate the diagram into VHDL, using component instantiation for HAs/FAs and dataflow for simple logic. - Include all temporary signals in the code, matching the diagram. - Ensure comments and readability. ### 4. **Testbench** - Write a VHDL testbench covering positive+positive, negative+negative, positive+negative, and negative+positive cases. - Include test cases where the sum is zero, and comment expected results. --- ## **Final Answer Summary** **Step 1:** You must design a 4-bit 1's complement adder with end-around carry, producing a 4-bit sum and a zero flag, using half/full adders. All signals must be clearly shown and labeled, and the design must be reflected in both a diagram and VHDL code. **Step 2:** Break your solution into four deliverables: 1. Draw the circuit diagram (with EAC and all signals). 2. Implement zero detection logic. 3. Write VHDL for the adder (with all signals and proper modeling). 4. Create a testbench covering all required cases, with expected outputs and comments. By following these steps, you address every requirement in the problem and grading rubric.