题目

  4bit超前进位加法器的逻辑表达式如下：

  $G_i$=$A_i$$B_i$，$P_i$=$A_i$$\oplus$$B_i$
  和：$S_i$=$P_i$$\oplus$$C_{i-1}$
  进位：$C_i$=$G_i$ + $P_i$$C_{i-1}$

  请用Verilog语言采用门级描述方式，实现此4bit超前进位加法器，接口电路如下：

答案

`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
);

wire [3:0]	G;
wire [3:0]	P;
wire [3:0]	C;

assign 	G = A_in & B_in;
assign	P = A_in ^ B_in;
assign  C[0] = G[0] | P[0] & C_1;
assign  C[1] = G[1] | P[1] & C[0];
assign  C[2] = G[2] | P[2] & C[1];
assign  C[3] = G[3] | P[3] & C[2];
assign	CO = C[3];

assign	S[0] = P[0] ^ C_1;
assign	S[1] = P[1] ^ C[0];
assign	S[2] = P[2] ^ C[1];
assign	S[3] = P[3] ^ C[2];

endmodule