Final Answer:
Implementing an 8-bit add/subtract in Verilog or VHDL using conditional selection (AS Sel) to perform addition (AS Sel = 0) or subtraction (AS Sel = 1) based on the operation selection. Utilizing signed, 2's-Complement numbers for OpA and OpB.
Explanation:
For this task, the implementation involves creating a module in Verilog or VHDL that takes in OpA and OpB as signed 8-bit inputs and AS Sel as a control signal. The conditional selection, controlled by AS Sel, allows for either addition or subtraction based on its value.
When AS Sel equals 0, the module performs addition, and when AS Sel equals 1, it triggers subtraction. The inputs OpA and OpB are assumed to be represented in 2's-Complement form to handle signed numbers.
The design needs to consider overflow conditions and utilize appropriate arithmetic logic for both addition and subtraction operations to handle negative numbers and carry-over scenarios.
This can be achieved by utilizing conditional statements within the Verilog or VHDL code.
When AS Sel is set to 0, the code would execute the addition operation, considering sign extension, carry, and overflow conditions. Conversely, when AS Sel is set to 1, the code would perform subtraction, taking into account borrow conditions for signed numbers in 2's-Complement representation. The resulting output will be the sum or difference based on the selected operation.
To ensure correctness and functionality, rigorous testing using testbenches with various input combinations should be carried out to verify the proper functioning of the designed module under different scenarios, covering edge cases and overflow conditions.