题解 | #4bit超前进位加法器电路#

`timescale 1ns/1ns

module lca_4(
	input		[3:0]       A_in  ,
	input	    [3:0]		B_in  ,
    input                   C_1   ,
 
 	output	 wire			CO    ,
	output   wire [3:0]	    S
);

	reg [3:0] G, P, C;
    reg [3:0] Si;
    integer i;

    always @(*) begin
        // 初始化
        G = 4'b0;
        P = 4'b0;
        Si = 4'b0;
        C = 4'b0;

        // 计算第一个位
        G[0] = A_in[0] & B_in[0];
        P[0] = A_in[0] ^ B_in[0];
        Si[0] = P[0] ^ C_1;
        C[0] = G[0] | (P[0] & C_1);

        // 计算其他位
        for (i = 1; i < 4; i = i + 1) begin
            G[i] = A_in[i] & B_in[i];
            P[i] = A_in[i] ^ B_in[i];
            Si[i] = P[i] ^ C[i-1];
            C[i] = G[i] | (P[i] & C[i-1]);
        end
    end

    assign S = Si;
    assign CO = C[3];
    
endmodule