题解 | #4bit超前进位加法器电路#
4bit超前进位加法器电路
https://www.nowcoder.com/practice/4d5b6dc4bb2848039da2ee40f9738363
`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;//生成进位项
wire [3:0] p;//传播进位项
wire C3;
assign g = A_in & B_in;
assign p = A_in ^ B_in;
assign C3 = g[3] | (p[3]&(g[2] | (p[2]&(g[1] | (p[1]&(g[0] | (p[0]&C_1)))))));
assign S[0] = p[0] ^ C_1;
assign S[1] = p[1] ^ (g[0] | (p[0]&C_1));
assign S[2] = p[2] ^ (g[1] | (p[1]&(g[0] | (p[0]&C_1))));
assign S[3] = p[3] ^ (g[2] | (p[2]&(g[1] | (p[1]&(g[0] | (p[0]&C_1))))));
//assign C2 = g[2] | (p[2]&(g[1] | (p[1]&(g[0] | (p[0]&C_1)))));
//assign C1 = g[1] | (p[1]&(g[0] | (p[0]&C_1)));
//assign C0 = g[0] | (p[0]&C_1);
assign CO = C3;
endmodule
超前进位的特点就是深度浅，运行速度快。但是面积大，比较复杂。可以直接根据输入比特进行计算，不需要中间变量
