configurable_mult.v

/**
 * Configurable Multiplier
 * 
 * This module implements a configurable multiplier that can perform both signed
 * and unsigned multiplication. It supports both compile-time and runtime
 * configuration of the sign mode.
 * 
 * Key Features:
 * - Signed/unsigned mode: Can switch between signed and unsigned multiplication
 * - Compile-time configurable: SIGNED_MODE parameter
 * - Runtime configurable: sign_mode input signal
 * - Two's complement: Properly handles signed two's complement arithmetic
 * - Configurable width: Any bit width via WIDTH parameter
 * 
 * Sign Mode:
 * - SIGNED_MODE = 0, sign_mode = 0: Unsigned multiplication
 * - SIGNED_MODE = 1, sign_mode = 1: Signed multiplication
 * - Either parameter or signal can enable signed mode
 * 
 * Signed Multiplication:
 * - Inputs are sign-extended before multiplication
 * - Result is properly sign-extended to 2×WIDTH bits
 * - Handles two's complement correctly
 * 
 * Unsigned Multiplication:
 * - Standard unsigned multiplication
 * - Result is zero-extended to 2×WIDTH bits
 * 
 * Use Cases:
 * - Arithmetic units in processors
 * - Digital signal processing
 * - Graphics processing
 * - Mathematical computations
 * 
 * @param WIDTH Width of input operands (default: 8 bits)
 *              Product width is 2×WIDTH bits
 * @param SIGNED_MODE Compile-time sign mode: 0=unsigned, 1=signed (default: 0)
 * 
 * @input a[WIDTH-1:0] First operand
 * @input b[WIDTH-1:0] Second operand
 * @input sign_mode Runtime sign mode control: 0=unsigned, 1=signed
 * @output product[2*WIDTH-1:0] Multiplication result
 */
module configurable_mult #(
    parameter WIDTH = 8,                     // Width of each input operand
    parameter SIGNED_MODE = 0                // 0 for unsigned, 1 for signed multiplication
) (
    input wire [WIDTH-1:0] a,                // Input operand A
    input wire [WIDTH-1:0] b,                // Input operand B
    input wire sign_mode,                    // Dynamic sign mode control (0=unsigned, 1=signed)
    output reg [2*WIDTH-1:0] product         // Result of multiplication
);

    // ============================================================================
    // Sign Mode Determination
    // ============================================================================
    // Signed mode is enabled if either compile-time parameter or runtime signal is set
    // This allows flexibility: can be configured at compile time or runtime
    wire is_signed = SIGNED_MODE || sign_mode;
    
    // ============================================================================
    // Multiplication Logic
    // ============================================================================
    // Performs multiplication based on sign mode
    always @(*) begin
        if (is_signed) begin
            // ====================================================================
            // Signed Multiplication
            // ====================================================================
            // Sign-extend inputs before multiplication
            // Sign extension: replicate MSB to extend to wider width
            // $signed() cast ensures proper two's complement interpretation
            // Result is automatically sign-extended to 2×WIDTH bits
            product = $signed({{1{a[WIDTH-1]}}, a}) * $signed({{1{b[WIDTH-1]}}, b});
        end else begin
            // ====================================================================
            // Unsigned Multiplication
            // ====================================================================
            // Standard unsigned multiplication
            // Result is zero-extended to 2×WIDTH bits
            product = a * b;
        end
    end
endmodule